mcs/class/corlib/System/TimeZoneInfo.cs

   1
   2 /*
   3  * System.TimeZoneInfo
   4  *
   5  * Author(s)
   6  *      Stephane Delcroix <stephane@delcroix.org>
   7  *
   8  * Copyright 2011 Xamarin Inc.
   9  *
  10  * Permission is hereby granted, free of charge, to any person obtaining
  11  * a copy of this software and associated documentation files (the
  12  * "Software"), to deal in the Software without restriction, including
  13  * without limitation the rights to use, copy, modify, merge, publish,
  14  * distribute, sublicense, and/or sell copies of the Software, and to
  15  * permit persons to whom the Software is furnished to do so, subject to
  16  * the following conditions:
  17  *
  18  * The above copyright notice and this permission notice shall be
  19  * included in all copies or substantial portions of the Software.
  20  *
  21  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22  * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25  * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26  * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27  * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28  */
  29
  30 using System;
  31 using System.Runtime.CompilerServices;
  32 using System.Threading;
  33 using System.Collections.Generic;
  34 using System.Collections.ObjectModel;
  35 using System.Runtime.Serialization;
  36 using System.Text;
  37 using System.Globalization;
  38
  39 #if LIBC || MONODROID
  40 using System.IO;
  41 using Mono;
  42 #endif
  43
  44 using Microsoft.Win32;
  45
  46 namespace System
  47 {
  48 #if MOBILE
  49         [TypeForwardedFrom (Consts.AssemblySystem_Core)]
  50 #else
  51         [TypeForwardedFrom (Consts.AssemblySystemCore_3_5)]
  52 #endif
  53         [SerializableAttribute]
  54         public
  55         sealed partial class TimeZoneInfo : IEquatable<TimeZoneInfo>, ISerializable, IDeserializationCallback
  56         {
  57                 TimeSpan baseUtcOffset;
  58                 public TimeSpan BaseUtcOffset {
  59                         get { return baseUtcOffset; }
  60                 }
  61
  62                 string daylightDisplayName;
  63                 public string DaylightName {
  64                         get {
  65                                 return supportsDaylightSavingTime
  66                                         ? daylightDisplayName
  67                                         : string.Empty;
  68                         }
  69                 }
  70
  71                 string displayName;
  72                 public string DisplayName {
  73                         get { return displayName; }
  74                 }
  75
  76                 string id;
  77                 public string Id {
  78                         get { return id; }
  79                 }
  80
  81                 static TimeZoneInfo local;
  82                 public static TimeZoneInfo Local {
  83                         get {
  84                                 var l = local;
  85                                 if (l == null) {
  86                                         l = CreateLocal ();
  87                                         if (l == null)
  88                                                 throw new TimeZoneNotFoundException ();
  89
  90                                         if (Interlocked.CompareExchange (ref local, l, null) != null)
  91                                                 l = local;
  92                                 }
  93
  94                                 return l;
  95                         }
  96                 }
  97
  98                 /*
  99                         TimeZone transitions are stored when there is a change on the base offset.
 100                 */
 101                 private List<KeyValuePair<DateTime, TimeType>> transitions;
 102
 103                 static TimeZoneInfo CreateLocal ()
 104                 {
 105 #if MONODROID
 106                         return AndroidTimeZones.Local;
 107 #elif MONOTOUCH
 108                         using (Stream stream = GetMonoTouchData (null)) {
 109                                 return BuildFromStream ("Local", stream);
 110                         }
 111 #else
 112 #if !NET_2_1
 113                         if (IsWindows && LocalZoneKey != null) {
 114                                 string name = (string)LocalZoneKey.GetValue ("TimeZoneKeyName");
 115                                 if (name == null)
 116                                         name = (string)LocalZoneKey.GetValue ("StandardName"); // windows xp
 117                                 name = TrimSpecial (name);
 118                                 if (name != null)
 119                                         return TimeZoneInfo.FindSystemTimeZoneById (name);
 120                         }
 121 #endif
 122
 123                         var tz = Environment.GetEnvironmentVariable ("TZ");
 124                         if (tz != null) {
 125                                 if (tz == String.Empty)
 126                                         return Utc;
 127                                 try {
 128                                         return FindSystemTimeZoneByFileName (tz, Path.Combine (TimeZoneDirectory, tz));
 129                                 } catch {
 130                                         return Utc;
 131                                 }
 132                         }
 133
 134                         try {
 135                                 return FindSystemTimeZoneByFileName ("Local", "/etc/localtime");
 136                         } catch {
 137                                 try {
 138                                         return FindSystemTimeZoneByFileName ("Local", Path.Combine (TimeZoneDirectory, "localtime"));
 139                                 } catch {
 140                                         return null;
 141                                 }
 142                         }
 143 #endif
 144                 }
 145
 146                 string standardDisplayName;
 147                 public string StandardName {
 148                         get { return standardDisplayName; }
 149                 }
 150
 151                 bool supportsDaylightSavingTime;
 152                 public bool SupportsDaylightSavingTime {
 153                         get  { return supportsDaylightSavingTime; }
 154                 }
 155
 156                 static TimeZoneInfo utc;
 157                 public static TimeZoneInfo Utc {
 158                         get {
 159                                 if (utc == null)
 160                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 161                                 return utc;
 162                         }
 163                 }
 164 #if LIBC
 165                 static string timeZoneDirectory;
 166                 static string TimeZoneDirectory {
 167                         get {
 168                                 if (timeZoneDirectory == null)
 169                                         timeZoneDirectory = "/usr/share/zoneinfo";
 170                                 return timeZoneDirectory;
 171                         }
 172                         set {
 173                                 ClearCachedData ();
 174                                 timeZoneDirectory = value;
 175                         }
 176                 }
 177 #endif
 178                 private AdjustmentRule [] adjustmentRules;
 179
 180 #if !NET_2_1
 181                 /// <summary>
 182                 /// Determine whether windows of not (taken Stephane Delcroix's code)
 183                 /// </summary>
 184                 private static bool IsWindows
 185                 {
 186                         get {
 187                                 int platform = (int) Environment.OSVersion.Platform;
 188                                 return ((platform != 4) && (platform != 6) && (platform != 128));
 189                         }
 190                 }
 191
 192                 /// <summary>
 193                 /// Needed to trim misc garbage in MS registry keys
 194                 /// </summary>
 195                 private static string TrimSpecial (string str)
 196                 {
 197                         if (str == null)
 198                                 return str;
 199                         var Istart = 0;
 200                         while (Istart < str.Length && !char.IsLetterOrDigit(str[Istart])) Istart++;
 201                         var Iend = str.Length - 1;
 202                         while (Iend > Istart && !char.IsLetterOrDigit(str[Iend])) Iend--;
 203
 204                         return str.Substring (Istart, Iend-Istart+1);
 205                 }
 206
 207                 static RegistryKey timeZoneKey;
 208                 static RegistryKey TimeZoneKey {
 209                         get {
 210                                 if (timeZoneKey != null)
 211                                         return timeZoneKey;
 212                                 if (!IsWindows)
 213                                         return null;
 214
 215                                 return timeZoneKey = Registry.LocalMachine.OpenSubKey (
 216                                         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 217                                         false);
 218                         }
 219                 }
 220
 221                 static RegistryKey localZoneKey;
 222                 static RegistryKey LocalZoneKey {
 223                         get {
 224                                 if (localZoneKey != null)
 225                                         return localZoneKey;
 226
 227                                 if (!IsWindows)
 228                                         return null;
 229
 230                                 return localZoneKey = Registry.LocalMachine.OpenSubKey (
 231                                         "SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation", false);
 232                         }
 233                 }
 234 #endif
 235
 236                 public static void ClearCachedData ()
 237                 {
 238                         local = null;
 239                         utc = null;
 240                         systemTimeZones = null;
 241                 }
 242
 243                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 244                 {
 245                         return ConvertTime (dateTime, dateTime.Kind == DateTimeKind.Utc ? TimeZoneInfo.Utc : TimeZoneInfo.Local, destinationTimeZone);
 246                 }
 247
 248                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 249                 {
 250                         if (sourceTimeZone == null)
 251                                 throw new ArgumentNullException ("sourceTimeZone");
 252
 253                         if (destinationTimeZone == null)
 254                                 throw new ArgumentNullException ("destinationTimeZone");
 255
 256                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 257                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 258
 259                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 260                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 261
 262                         if (sourceTimeZone.IsInvalidTime (dateTime))
 263                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 264
 265                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 266                                 return dateTime;
 267
 268                         DateTime utc = ConvertTimeToUtc (dateTime, sourceTimeZone);
 269
 270                         if (destinationTimeZone != TimeZoneInfo.Utc) {
 271                                 utc = ConvertTimeFromUtc (utc, destinationTimeZone);
 272                                 if (dateTime.Kind == DateTimeKind.Unspecified)
 273                                         return DateTime.SpecifyKind (utc, DateTimeKind.Unspecified);
 274                         }
 275
 276                         return utc;
 277                 }
 278
 279                 public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 280                 {
 281                         if (destinationTimeZone == null)
 282                                 throw new ArgumentNullException("destinationTimeZone");
 283
 284                         var utcDateTime = dateTimeOffset.UtcDateTime;
 285                         AdjustmentRule rule = destinationTimeZone.GetApplicableRule (utcDateTime);
 286
 287                         if (rule != null && destinationTimeZone.IsDaylightSavingTime(utcDateTime)) {
 288                                 var offset = destinationTimeZone.BaseUtcOffset + rule.DaylightDelta;
 289                                 return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + offset, offset);
 290                         }
 291                         else {
 292                                 return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + destinationTimeZone.BaseUtcOffset, destinationTimeZone.BaseUtcOffset);
 293                         }
 294                 }
 295
 296                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 297                 {
 298                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 299                 }
 300
 301                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 302                 {
 303                         return ConvertTime (dateTime, FindSystemTimeZoneById (sourceTimeZoneId), FindSystemTimeZoneById (destinationTimeZoneId));
 304                 }
 305
 306                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 307                 {
 308                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 309                 }
 310
 311                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 312                 {
 313                         if (dateTime.Kind == DateTimeKind.Local)
 314                                 throw new ArgumentException ("Kind property of dateTime is Local");
 315
 316                         if (this == TimeZoneInfo.Utc)
 317                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 318
 319                         //FIXME: do not rely on DateTime implementation !
 320                         if (this == TimeZoneInfo.Local)
 321                         {
 322                                 return dateTime.ToLocalTime ();
 323                         }
 324
 325
 326                         AdjustmentRule rule = GetApplicableRule (dateTime);
 327                         if (rule != null && IsDaylightSavingTime (DateTime.SpecifyKind (dateTime, DateTimeKind.Utc)))
 328                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset + rule.DaylightDelta , DateTimeKind.Unspecified);
 329                         else
 330                                 return DateTime.SpecifyKind (dateTime + BaseUtcOffset, DateTimeKind.Unspecified);
 331                 }
 332
 333                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 334                 {
 335                         if (destinationTimeZone == null)
 336                                 throw new ArgumentNullException ("destinationTimeZone");
 337
 338                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 339                 }
 340
 341                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 342                 {
 343                         if (dateTime.Kind == DateTimeKind.Utc)
 344                                 return dateTime;
 345
 346                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local);
 347                 }
 348
 349                 static internal DateTime ConvertTimeToUtc(DateTime dateTime, TimeZoneInfoOptions flags)
 350                 {
 351                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local, flags);
 352                 }
 353
 354                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 355                 {
 356                         return ConvertTimeToUtc (dateTime, sourceTimeZone, TimeZoneInfoOptions.None);
 357                 }
 358
 359                 static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfoOptions flags)
 360                 {
 361                         if ((flags & TimeZoneInfoOptions.NoThrowOnInvalidTime) == 0) {
 362                                 if (sourceTimeZone == null)
 363                                         throw new ArgumentNullException ("sourceTimeZone");
 364
 365                                 if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 366                                         throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 367
 368                                 if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 369                                         throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 370
 371                                 if (sourceTimeZone.IsInvalidTime (dateTime))
 372                                         throw new ArgumentException ("dateTime parameter is an invalid time");
 373                         }
 374
 375                         if (dateTime.Kind == DateTimeKind.Utc)
 376                                 return dateTime;
 377
 378                         if (sourceTimeZone.IsAmbiguousTime (dateTime) || !sourceTimeZone.IsDaylightSavingTime (dateTime)) {
 379                                 var ticks = dateTime.Ticks - sourceTimeZone.BaseUtcOffset.Ticks;
 380                                 if (ticks < DateTime.MinValue.Ticks)
 381                                         ticks = DateTime.MinValue.Ticks;
 382                                 else if (ticks > DateTime.MaxValue.Ticks)
 383                                         ticks = DateTime.MaxValue.Ticks;
 384
 385                                 return new DateTime (ticks, DateTimeKind.Utc);
 386                         }
 387
 388                                 AdjustmentRule rule = sourceTimeZone.GetApplicableRule (dateTime);
 389                                 if (rule != null)
 390                                         return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset - rule.DaylightDelta, DateTimeKind.Utc);
 391                                 else
 392                                         return DateTime.SpecifyKind (dateTime - sourceTimeZone.BaseUtcOffset, DateTimeKind.Utc);
 393
 394                 }
 395
 396                 static internal TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out Boolean isAmbiguousLocalDst)
 397                 {
 398                         bool isDaylightSavings;
 399                         return GetUtcOffsetFromUtc(time, TimeZoneInfo.Local, out isDaylightSavings, out isAmbiguousLocalDst);
 400                 }
 401
 402                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 403                 {
 404                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 405                 }
 406
 407                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 408                 {
 409                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 410                 }
 411
 412                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 413                 {
 414                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 415                 }
 416
 417                 public override bool Equals (object obj)
 418                 {
 419                         return Equals (obj as TimeZoneInfo);
 420                 }
 421
 422                 public bool Equals (TimeZoneInfo other)
 423                 {
 424                         if (other == null)
 425                                 return false;
 426
 427                         return other.Id == this.Id && HasSameRules (other);
 428                 }
 429
 430                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 431                 {
 432                         //FIXME: this method should check for cached values in systemTimeZones
 433                         if (id == null)
 434                                 throw new ArgumentNullException ("id");
 435 #if !NET_2_1
 436                         if (TimeZoneKey != null)
 437                         {
 438                                 if (id == "Coordinated Universal Time")
 439                                         id = "UTC"; //windows xp exception for "StandardName" property
 440                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 441                                 if (key == null)
 442                                         throw new TimeZoneNotFoundException ();
 443                                 return FromRegistryKey(id, key);
 444                         }
 445 #endif
 446                         // Local requires special logic that already exists in the Local property (bug #326)
 447                         if (id == "Local")
 448                                 return Local;
 449 #if MONOTOUCH
 450                         using (Stream stream = GetMonoTouchData (id)) {
 451                                 return BuildFromStream (id, stream);
 452                         }
 453 #elif MONODROID
 454                         var timeZoneInfo = AndroidTimeZones.GetTimeZone (id, id);
 455                         if (timeZoneInfo == null)
 456                                 throw new TimeZoneNotFoundException ();
 457                         return timeZoneInfo;
 458 #elif LIBC
 459                         string filepath = Path.Combine (TimeZoneDirectory, id);
 460                         return FindSystemTimeZoneByFileName (id, filepath);
 461 #else
 462                         throw new NotImplementedException ();
 463 #endif
 464                 }
 465
 466 #if LIBC
 467                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 468                 {
 469                         if (!File.Exists (filepath))
 470                                 throw new TimeZoneNotFoundException ();
 471
 472                         using (FileStream stream = File.OpenRead (filepath)) {
 473                                 return BuildFromStream (id, stream);
 474                         }
 475                 }
 476 #endif
 477 #if LIBC || MONOTOUCH
 478                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
 479
 480                 private static TimeZoneInfo BuildFromStream (string id, Stream stream)
 481                 {
 482                         byte [] buffer = new byte [BUFFER_SIZE];
 483                         int length = stream.Read (buffer, 0, BUFFER_SIZE);
 484
 485                         if (!ValidTZFile (buffer, length))
 486                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
 487
 488                         try {
 489                                 return ParseTZBuffer (id, buffer, length);
 490                         } catch (Exception e) {
 491                                 throw new InvalidTimeZoneException (e.Message);
 492                         }
 493                 }
 494 #endif
 495
 496 #if !NET_2_1
 497                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 498                 {
 499                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 500
 501                         if (reg_tzi == null)
 502                                 throw new InvalidTimeZoneException ();
 503
 504                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 505                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 506
 507                         string display_name = (string) key.GetValue ("Display");
 508                         string standard_name = (string) key.GetValue ("Std");
 509                         string daylight_name = (string) key.GetValue ("Dlt");
 510
 511                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 512
 513                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 514                         if (dst_key != null) {
 515                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 516                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 517                                 int year;
 518
 519                                 for (year=first_year; year<=last_year; year++) {
 520                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 521                                         if (dst_tzi != null) {
 522                                                 int start_year = year == first_year ? 1 : year;
 523                                                 int end_year = year == last_year ? 9999 : year;
 524                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 525                                         }
 526                                 }
 527                         }
 528                         else
 529                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 530
 531                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 532                 }
 533
 534                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 535                 {
 536                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 537                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 538
 539                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 540                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 541                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 542                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 543                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 544                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 545                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 546                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 547
 548                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 549                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 550                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 551                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 552                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 553                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 554                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 555                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 556
 557                         if (standard_month == 0 || daylight_month == 0)
 558                                 return;
 559
 560                         DateTime start_date;
 561                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 562                         TransitionTime start_transition_time;
 563
 564                         if (daylight_year == 0) {
 565                                 start_date = new DateTime (start_year, 1, 1);
 566                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 567                                         start_timeofday, daylight_month, daylight_day,
 568                                         (DayOfWeek) daylight_dayofweek);
 569                         }
 570                         else {
 571                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 572                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 573                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 574                                         start_timeofday, daylight_month, daylight_day);
 575                         }
 576
 577                         DateTime end_date;
 578                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 579                         TransitionTime end_transition_time;
 580
 581                         if (standard_year == 0) {
 582                                 end_date = new DateTime (end_year, 12, 31);
 583                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 584                                         end_timeofday, standard_month, standard_day,
 585                                         (DayOfWeek) standard_dayofweek);
 586                         }
 587                         else {
 588                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 589                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 590                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 591                                         end_timeofday, standard_month, standard_day);
 592                         }
 593
 594                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 595
 596                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 597                                 start_date, end_date, daylight_delta,
 598                                 start_transition_time, end_transition_time));
 599                 }
 600 #endif
 601
 602                 public AdjustmentRule [] GetAdjustmentRules ()
 603                 {
 604                         if (!supportsDaylightSavingTime)
 605                                 return new AdjustmentRule [0];
 606                         else
 607                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 608                 }
 609
 610                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 611                 {
 612                         if (!IsAmbiguousTime (dateTime))
 613                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 614
 615                         AdjustmentRule rule = GetApplicableRule (dateTime);
 616                         if (rule != null)
 617                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 618                         else
 619                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 620                 }
 621
 622                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 623                 {
 624                         if (!IsAmbiguousTime (dateTimeOffset))
 625                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 626
 627                         throw new NotImplementedException ();
 628                 }
 629
 630                 public override int GetHashCode ()
 631                 {
 632                         int hash_code = Id.GetHashCode ();
 633                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 634                                 hash_code ^= rule.GetHashCode ();
 635                         return hash_code;
 636                 }
 637
 638                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 639                 {
 640                         if (info == null)
 641                                 throw new ArgumentNullException ("info");
 642                         info.AddValue ("Id", id);
 643                         info.AddValue ("DisplayName", displayName);
 644                         info.AddValue ("StandardName", standardDisplayName);
 645                         info.AddValue ("DaylightName", daylightDisplayName);
 646                         info.AddValue ("BaseUtcOffset", baseUtcOffset);
 647                         info.AddValue ("AdjustmentRules", adjustmentRules);
 648                         info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
 649                 }
 650
 651                 //FIXME: change this to a generic Dictionary and allow caching for FindSystemTimeZoneById
 652                 private static List<TimeZoneInfo> systemTimeZones;
 653                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 654                 {
 655                         if (systemTimeZones == null) {
 656                                 systemTimeZones = new List<TimeZoneInfo> ();
 657 #if !NET_2_1
 658                                 if (TimeZoneKey != null) {
 659                                         foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
 660                                                 try {
 661                                                         systemTimeZones.Add (FindSystemTimeZoneById (id));
 662                                                 } catch {}
 663                                         }
 664
 665                                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 666                                 }
 667 #endif
 668 #if MONODROID
 669                         foreach (string id in AndroidTimeZones.GetAvailableIds ()) {
 670                                 var tz = AndroidTimeZones.GetTimeZone (id, id);
 671                                 if (tz != null)
 672                                         systemTimeZones.Add (tz);
 673                         }
 674 #elif MONOTOUCH
 675                                 if (systemTimeZones.Count == 0) {
 676                                         foreach (string name in GetMonoTouchNames ()) {
 677                                                 using (Stream stream = GetMonoTouchData (name, false)) {
 678                                                         if (stream == null)
 679                                                                 continue;
 680                                                         systemTimeZones.Add (BuildFromStream (name, stream));
 681                                                 }
 682                                         }
 683                                 }
 684 #elif LIBC
 685                                 string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 686                                 foreach (string continent in continents) {
 687                                         try {
 688                                                 foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 689                                                         try {
 690                                                                 string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 691                                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 692                                                         } catch (ArgumentNullException) {
 693                                                         } catch (TimeZoneNotFoundException) {
 694                                                         } catch (InvalidTimeZoneException) {
 695                                                         } catch (Exception) {
 696                                                                 throw;
 697                                                         }
 698                                                 }
 699                                         } catch {}
 700                                 }
 701 #else
 702                                 throw new NotImplementedException ("This method is not implemented for this platform");
 703 #endif
 704                         }
 705                         return new ReadOnlyCollection<TimeZoneInfo> (systemTimeZones);
 706                 }
 707
 708                 public TimeSpan GetUtcOffset (DateTime dateTime)
 709                 {
 710                         bool isDST;
 711                         return GetUtcOffset (dateTime, out isDST);
 712                 }
 713
 714                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 715                 {
 716                         throw new NotImplementedException ();
 717                 }
 718
 719                 private TimeSpan GetUtcOffset (DateTime dateTime, out bool isDST)
 720                 {
 721                         isDST = false;
 722
 723                         TimeZoneInfo tz = this;
 724                         if (dateTime.Kind == DateTimeKind.Utc)
 725                                 tz = TimeZoneInfo.Utc;
 726
 727                         if (dateTime.Kind == DateTimeKind.Local)
 728                                 tz = TimeZoneInfo.Local;
 729
 730                         bool isTzDst;
 731                         var tzOffset = GetUtcOffset (dateTime, tz, out isTzDst);
 732
 733                         if (tz == this) {
 734                                 isDST = isTzDst;
 735                                 return tzOffset;
 736                         }
 737
 738                         var utcTicks = dateTime.Ticks - tzOffset.Ticks;
 739                         if (utcTicks < 0 || utcTicks > DateTime.MaxValue.Ticks)
 740                                 return BaseUtcOffset;
 741
 742                         var utcDateTime = new DateTime (utcTicks, DateTimeKind.Utc);
 743
 744                         return GetUtcOffset (utcDateTime, this, out isDST);
 745                 }
 746
 747                 private static TimeSpan GetUtcOffset (DateTime dateTime, TimeZoneInfo tz, out bool isDST)
 748                 {
 749                         if (dateTime.Kind == DateTimeKind.Local && tz != TimeZoneInfo.Local)
 750                                 throw new Exception ();
 751
 752                         isDST = false;
 753
 754                         if (tz == TimeZoneInfo.Utc)
 755                                 return TimeSpan.Zero;
 756
 757                         TimeSpan offset;
 758                         if (tz.TryGetTransitionOffset(dateTime, out offset, out isDST))
 759                                 return offset;
 760
 761                         if (dateTime.Kind == DateTimeKind.Utc) {
 762                                 var utcRule = tz.GetApplicableRule (dateTime);
 763                                 if (utcRule != null && tz.IsInDST (utcRule, dateTime)) {
 764                                         isDST = true;
 765                                         return tz.BaseUtcOffset + utcRule.DaylightDelta;
 766                                 }
 767
 768                                 return tz.BaseUtcOffset;
 769                         }
 770
 771                         var stdTicks = dateTime.Ticks - tz.BaseUtcOffset.Ticks;
 772                         if (stdTicks < 0 || stdTicks > DateTime.MaxValue.Ticks)
 773                                 return tz.BaseUtcOffset;
 774
 775                         var stdUtcDateTime = new DateTime (stdTicks, DateTimeKind.Utc);
 776                         var tzRule = tz.GetApplicableRule (stdUtcDateTime);
 777
 778                         DateTime dstUtcDateTime = DateTime.MinValue;
 779                         if (tzRule != null) {
 780                                 var dstTicks = stdUtcDateTime.Ticks - tzRule.DaylightDelta.Ticks;
 781                                 if (dstTicks < 0 || dstTicks > DateTime.MaxValue.Ticks)
 782                                         return tz.BaseUtcOffset;
 783
 784                                 dstUtcDateTime = new DateTime (dstTicks, DateTimeKind.Utc);
 785                         }
 786
 787                         if (tzRule != null && tz.IsInDST (tzRule, stdUtcDateTime) && tz.IsInDST (tzRule, dstUtcDateTime)) {
 788                                 isDST = true;
 789                                 return tz.BaseUtcOffset + tzRule.DaylightDelta;
 790                         }
 791
 792                         return tz.BaseUtcOffset;
 793                 }
 794
 795                 public bool HasSameRules (TimeZoneInfo other)
 796                 {
 797                         if (other == null)
 798                                 throw new ArgumentNullException ("other");
 799
 800                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 801                                 return false;
 802
 803                         if (this.adjustmentRules == null)
 804                                 return true;
 805
 806                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 807                                 return false;
 808
 809                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 810                                 return false;
 811
 812                         for (int i = 0; i < adjustmentRules.Length; i++) {
 813                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 814                                         return false;
 815                         }
 816
 817                         return true;
 818                 }
 819
 820                 public bool IsAmbiguousTime (DateTime dateTime)
 821                 {
 822                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 823                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 824
 825                         if (this == TimeZoneInfo.Utc)
 826                                 return false;
 827
 828                         if (dateTime.Kind == DateTimeKind.Utc)
 829                                 dateTime = ConvertTimeFromUtc (dateTime);
 830
 831                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 832                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 833
 834                         AdjustmentRule rule = GetApplicableRule (dateTime);
 835                         if (rule != null) {
 836                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 837                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 838                                         return true;
 839                         }
 840
 841                         return false;
 842                 }
 843
 844                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 845                 {
 846                         throw new NotImplementedException ();
 847                 }
 848
 849                 private bool IsInDST (AdjustmentRule rule, DateTime dateTime)
 850                 {
 851                         // Check whether we're in the dateTime year's DST period
 852                         if (IsInDSTForYear (rule, dateTime, dateTime.Year))
 853                                 return true;
 854
 855                         // We might be in the dateTime previous year's DST period
 856                         return IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
 857                 }
 858
 859                 bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
 860                 {
 861                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
 862                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 863                         if (dateTime.Kind == DateTimeKind.Utc) {
 864                                 DST_start -= BaseUtcOffset;
 865                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 866                         }
 867
 868                         return (dateTime >= DST_start && dateTime < DST_end);
 869                 }
 870
 871                 public bool IsDaylightSavingTime (DateTime dateTime)
 872                 {
 873                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 874                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 875
 876                         if (this == TimeZoneInfo.Utc)
 877                                 return false;
 878
 879                         if (!SupportsDaylightSavingTime)
 880                                 return false;
 881
 882                         bool isDst;
 883                         GetUtcOffset (dateTime, out isDst);
 884
 885                         return isDst;
 886                 }
 887
 888                 internal bool IsDaylightSavingTime (DateTime dateTime, TimeZoneInfoOptions flags)
 889                 {
 890                         return IsDaylightSavingTime (dateTime);
 891                 }
 892
 893                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 894                 {
 895                         throw new NotImplementedException ();
 896                 }
 897
 898                 void IDeserializationCallback.OnDeserialization (object sender)
 899                 {
 900                         try {
 901                                         TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
 902                                 } catch (ArgumentException ex) {
 903                                         throw new SerializationException ("invalid serialization data", ex);
 904                                 }
 905                 }
 906
 907                 private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
 908                 {
 909                         if (id == null)
 910                                 throw new ArgumentNullException ("id");
 911
 912                         if (id == String.Empty)
 913                                 throw new ArgumentException ("id parameter is an empty string");
 914
 915                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 916                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 917
 918                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 919                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 920
 921 #if STRICT
 922                         if (id.Length > 32)
 923                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 924 #endif
 925
 926                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 927                                 AdjustmentRule prev = null;
 928                                 foreach (AdjustmentRule current in adjustmentRules) {
 929                                         if (current == null)
 930                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 931
 932                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 933                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 934                                                 throw new InvalidTimeZoneException ("Sum of baseUtcOffset and DaylightDelta of one or more object in adjustmentRules array is greater than 14 or less than -14 hours;");
 935
 936                                         if (prev != null && prev.DateStart > current.DateStart)
 937                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
 938
 939                                         if (prev != null && prev.DateEnd > current.DateStart)
 940                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
 941
 942                                         if (prev != null && prev.DateEnd == current.DateStart)
 943                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
 944
 945                                         prev = current;
 946                                 }
 947                         }
 948                 }
 949
 950                 public override string ToString ()
 951                 {
 952                         return DisplayName;
 953                 }
 954
 955                 private TimeZoneInfo (SerializationInfo info, StreamingContext context)
 956                 {
 957                         if (info == null)
 958                                 throw new ArgumentNullException ("info");
 959                         id = (string) info.GetValue ("Id", typeof (string));
 960                         displayName = (string) info.GetValue ("DisplayName", typeof (string));
 961                         standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
 962                         daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
 963                         baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
 964                         adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
 965                         supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
 966                 }
 967
 968                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 969                 {
 970                         if (id == null)
 971                                 throw new ArgumentNullException ("id");
 972
 973                         if (id == String.Empty)
 974                                 throw new ArgumentException ("id parameter is an empty string");
 975
 976                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
 977                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
 978
 979                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
 980                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
 981
 982 #if STRICT
 983                         if (id.Length > 32)
 984                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
 985 #endif
 986
 987                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
 988
 989                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
 990                                 AdjustmentRule prev = null;
 991                                 foreach (AdjustmentRule current in adjustmentRules) {
 992                                         if (current == null)
 993                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
 994
 995                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
 996                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
 997                                                 throw new InvalidTimeZoneException ("Sum of baseUtcOffset and DaylightDelta of one or more object in adjustmentRules array is greater than 14 or less than -14 hours;");
 998
 999                                         if (prev != null && prev.DateStart > current.DateStart)
1000                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1001
1002                                         if (prev != null && prev.DateEnd > current.DateStart)
1003                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1004
1005                                         if (prev != null && prev.DateEnd == current.DateStart)
1006                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1007
1008                                         prev = current;
1009                                 }
1010                         } else {
1011                                 supportsDaylightSavingTime = false;
1012                         }
1013
1014                         this.id = id;
1015                         this.baseUtcOffset = baseUtcOffset;
1016                         this.displayName = displayName ?? id;
1017                         this.standardDisplayName = standardDisplayName ?? id;
1018                         this.daylightDisplayName = daylightDisplayName;
1019                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
1020                         this.adjustmentRules = adjustmentRules;
1021                 }
1022
1023                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
1024                 {
1025                         //Applicable rules are in standard time
1026                         DateTime date = dateTime;
1027
1028                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
1029                                 date = date.ToUniversalTime () + BaseUtcOffset;
1030                         else if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc)
1031                                 date = date + BaseUtcOffset;
1032
1033                         // get the date component of the datetime
1034                         date = date.Date;
1035
1036                         if (adjustmentRules != null) {
1037                                 foreach (AdjustmentRule rule in adjustmentRules) {
1038                                         if (rule.DateStart > date)
1039                                                 return null;
1040                                         if (rule.DateEnd < date)
1041                                                 continue;
1042                                         return rule;
1043                                 }
1044                         }
1045                         return null;
1046                 }
1047
1048                 private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset,out bool isDst)
1049                 {
1050                         offset = BaseUtcOffset;
1051                         isDst = false;
1052
1053                         if (transitions == null)
1054                                 return false;
1055
1056                         //Transitions are in UTC
1057                         DateTime date = dateTime;
1058
1059                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1060                                 var ticks = date.ToUniversalTime ().Ticks + BaseUtcOffset.Ticks;
1061                                 if (ticks < DateTime.MinValue.Ticks || ticks > DateTime.MaxValue.Ticks)
1062                                         return false;
1063
1064                                 date = new DateTime (ticks, DateTimeKind.Utc);
1065                         }
1066
1067                         if (dateTime.Kind != DateTimeKind.Utc) {
1068                                 var ticks = date.Ticks - BaseUtcOffset.Ticks;
1069                                 if (ticks < DateTime.MinValue.Ticks || ticks > DateTime.MaxValue.Ticks)
1070                                         return false;
1071
1072                                 date = new DateTime (ticks, DateTimeKind.Utc);
1073                         }
1074
1075                         for (var i =  transitions.Count - 1; i >= 0; i--) {
1076                                 var pair = transitions [i];
1077                                 DateTime ttime = pair.Key;
1078                                 TimeType ttype = pair.Value;
1079
1080                                 if (ttime > date)
1081                                         continue;
1082
1083                                 offset =  new TimeSpan (0, 0, ttype.Offset);
1084                                 isDst = ttype.IsDst;
1085
1086                                 return true;
1087                         }
1088
1089                         return false;
1090                 }
1091
1092                 private static DateTime TransitionPoint (TransitionTime transition, int year)
1093                 {
1094                         if (transition.IsFixedDateRule)
1095                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
1096
1097                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
1098                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first + 7) % 7;
1099                         if (day >  DateTime.DaysInMonth (year, transition.Month))
1100                                 day -= 7;
1101                         if (day < 1)
1102                                 day += 7;
1103                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
1104                 }
1105
1106                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
1107                 {
1108                         AdjustmentRule prev = null;
1109                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
1110                                 if (prev != null && prev.DateEnd > current.DateStart) {
1111                                         adjustmentRules.Remove (current);
1112                                 }
1113                                 prev = current;
1114                         }
1115                         return adjustmentRules;
1116                 }
1117
1118 #if LIBC || MONODROID
1119                 private static bool ValidTZFile (byte [] buffer, int length)
1120                 {
1121                         StringBuilder magic = new StringBuilder ();
1122
1123                         for (int i = 0; i < 4; i++)
1124                                 magic.Append ((char)buffer [i]);
1125
1126                         if (magic.ToString () != "TZif")
1127                                 return false;
1128
1129                         if (length >= BUFFER_SIZE)
1130                                 return false;
1131
1132                         return true;
1133                 }
1134
1135                 static int SwapInt32 (int i)
1136                 {
1137                         return (((i >> 24) & 0xff)
1138                                 | ((i >> 8) & 0xff00)
1139                                 | ((i << 8) & 0xff0000)
1140                                 | ((i << 24)));
1141                 }
1142
1143                 static int ReadBigEndianInt32 (byte [] buffer, int start)
1144                 {
1145                         int i = BitConverter.ToInt32 (buffer, start);
1146                         if (!BitConverter.IsLittleEndian)
1147                                 return i;
1148
1149                         return SwapInt32 (i);
1150                 }
1151
1152                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
1153                 {
1154                         //Reading the header. 4 bytes for magic, 16 are reserved
1155                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
1156                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
1157                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
1158                         int timecnt = ReadBigEndianInt32 (buffer, 32);
1159                         int typecnt = ReadBigEndianInt32 (buffer, 36);
1160                         int charcnt = ReadBigEndianInt32 (buffer, 40);
1161
1162                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
1163                                 throw new InvalidTimeZoneException ();
1164
1165                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
1166                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
1167                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
1168
1169                         if (time_types.Count == 0)
1170                                 throw new InvalidTimeZoneException ();
1171
1172                         if (time_types.Count == 1 && ((TimeType)time_types[0]).IsDst)
1173                                 throw new InvalidTimeZoneException ();
1174
1175                         TimeSpan baseUtcOffset = new TimeSpan (0);
1176                         TimeSpan dstDelta = new TimeSpan (0);
1177                         string standardDisplayName = null;
1178                         string daylightDisplayName = null;
1179                         bool dst_observed = false;
1180                         DateTime dst_start = DateTime.MinValue;
1181                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
1182                         bool storeTransition = false;
1183
1184                         for (int i = 0; i < transitions.Count; i++) {
1185                                 var pair = transitions [i];
1186                                 DateTime ttime = pair.Key;
1187                                 TimeType ttype = pair.Value;
1188                                 if (!ttype.IsDst) {
1189                                         if (standardDisplayName != ttype.Name)
1190                                                 standardDisplayName = ttype.Name;
1191                                         if (baseUtcOffset.TotalSeconds != ttype.Offset) {
1192                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
1193                                                 if (adjustmentRules.Count > 0) // We ignore AdjustmentRules but store transitions.
1194                                                         storeTransition = true;
1195                                                 adjustmentRules = new List<AdjustmentRule> ();
1196                                                 dst_observed = false;
1197                                         }
1198                                         if (dst_observed) {
1199                                                 //FIXME: check additional fields for this:
1200                                                 //most of the transitions are expressed in GMT
1201                                                 dst_start += baseUtcOffset;
1202                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
1203
1204                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
1205                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
1206                                                         dst_end -= new TimeSpan (24, 0, 0);
1207
1208                                                 DateTime dateStart, dateEnd;
1209                                                 if (dst_start.Month < 7)
1210                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
1211                                                 else
1212                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
1213
1214                                                 if (dst_end.Month >= 7)
1215                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
1216                                                 else
1217                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1218
1219
1220                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1221                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1222                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1223                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1224                                         }
1225                                         dst_observed = false;
1226                                 } else {
1227                                         if (daylightDisplayName != ttype.Name)
1228                                                 daylightDisplayName = ttype.Name;
1229                                         if (dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds)
1230                                                 dstDelta = new TimeSpan(0, 0, ttype.Offset) - baseUtcOffset;
1231
1232                                         dst_start = ttime;
1233                                         dst_observed = true;
1234                                 }
1235                         }
1236
1237                         TimeZoneInfo tz;
1238                         if (adjustmentRules.Count == 0 && !storeTransition) {
1239                                 TimeType t = (TimeType)time_types [0];
1240                                 if (standardDisplayName == null) {
1241                                         standardDisplayName = t.Name;
1242                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1243                                 }
1244                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1245                         } else {
1246                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1247                         }
1248
1249                         if (storeTransition)
1250                                 tz.transitions = transitions;
1251
1252                         return tz;
1253                 }
1254
1255                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1256                 {
1257                         var abbrevs = new Dictionary<int, string> ();
1258                         int abbrev_index = 0;
1259                         var sb = new StringBuilder ();
1260                         for (int i = 0; i < count; i++) {
1261                                 char c = (char) buffer [index + i];
1262                                 if (c != '\0')
1263                                         sb.Append (c);
1264                                 else {
1265                                         abbrevs.Add (abbrev_index, sb.ToString ());
1266                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1267                                         for (int j = 1; j < sb.Length; j++)
1268                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1269                                         abbrev_index = i + 1;
1270                                         sb = new StringBuilder ();
1271                                 }
1272                         }
1273                         return abbrevs;
1274                 }
1275
1276                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1277                 {
1278                         var types = new Dictionary<int, TimeType> (count);
1279                         for (int i = 0; i < count; i++) {
1280                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1281                                 byte is_dst = buffer [index + 6 * i + 4];
1282                                 byte abbrev = buffer [index + 6 * i + 5];
1283                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1284                         }
1285                         return types;
1286                 }
1287
1288                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1289                 {
1290                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1291                         for (int i = 0; i < count; i++) {
1292                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1293                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1294                                 byte ttype = buffer [index + 4 * count + i];
1295                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1296                         }
1297                         return list;
1298                 }
1299
1300                 static DateTime DateTimeFromUnixTime (long unix_time)
1301                 {
1302                         DateTime date_time = new DateTime (1970, 1, 1);
1303                         return date_time.AddSeconds (unix_time);
1304                 }
1305
1306 #region reference sources
1307         // Shortcut for TimeZoneInfo.Local.GetUtcOffset
1308         internal static TimeSpan GetLocalUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1309         {
1310             bool dst;
1311             return Local.GetUtcOffset (dateTime, out dst);
1312         }
1313
1314         internal TimeSpan GetUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1315         {
1316             bool dst;
1317             return GetUtcOffset (dateTime, out dst);
1318         }
1319
1320         // used by GetUtcOffsetFromUtc (DateTime.Now, DateTime.ToLocalTime) for max/min whole-day range checks
1321         private static DateTime s_maxDateOnly = new DateTime(9999, 12, 31);
1322         private static DateTime s_minDateOnly = new DateTime(1, 1, 2);
1323
1324         static internal TimeSpan GetUtcOffsetFromUtc (DateTime time, TimeZoneInfo zone, out Boolean isDaylightSavings, out Boolean isAmbiguousLocalDst)
1325         {
1326             isDaylightSavings = false;
1327             isAmbiguousLocalDst = false;
1328             TimeSpan baseOffset = zone.BaseUtcOffset;
1329             Int32 year;
1330             AdjustmentRule rule;
1331
1332             if (time > s_maxDateOnly) {
1333                 rule = zone.GetAdjustmentRuleForTime(DateTime.MaxValue);
1334                 year = 9999;
1335             }
1336             else if (time < s_minDateOnly) {
1337                 rule = zone.GetAdjustmentRuleForTime(DateTime.MinValue);
1338                 year = 1;
1339             }
1340             else {
1341                 DateTime targetTime = time + baseOffset;
1342                 year = time.Year;
1343                 rule = zone.GetAdjustmentRuleForTime(targetTime);
1344             }
1345
1346             if (rule != null) {
1347                 isDaylightSavings = GetIsDaylightSavingsFromUtc(time, year, zone.baseUtcOffset, rule, out isAmbiguousLocalDst);
1348                 baseOffset += (isDaylightSavings ? rule.DaylightDelta : TimeSpan.Zero /* */);
1349             }
1350
1351             return baseOffset;
1352         }
1353
1354         // assumes dateTime is in the current time zone's time
1355         private AdjustmentRule GetAdjustmentRuleForTime(DateTime dateTime) {
1356             if (adjustmentRules == null || adjustmentRules.Length == 0) {
1357                 return null;
1358             }
1359
1360 #if WINXP_AND_WIN2K3_SUPPORT
1361             // On pre-Vista versions of Windows if you run "cmd /c date" or "cmd /c time" to update the system time
1362             // the operating system doesn't pick up the correct time zone adjustment rule (it stays on the currently loaded rule).
1363             // We need to use the OS API data in this scenario instead of the loaded adjustment rules from the registry for
1364             // consistency.  Otherwise DateTime.Now might not match the time displayed in the system tray.
1365             if (!Environment.IsWindowsVistaOrAbove && s_cachedData.GetCorrespondingKind(this) == DateTimeKind.Local) {
1366                 return s_cachedData.GetOneYearLocalFromLocal(dateTime.Year).rule;
1367             }
1368 #endif
1369             // Only check the whole-date portion of the dateTime -
1370             // This is because the AdjustmentRule DateStart & DateEnd are stored as
1371             // Date-only values {4/2/2006 - 10/28/2006} but actually represent the
1372             // time span {4/2/2006@00:00:00.00000 - 10/28/2006@23:59:59.99999}
1373             DateTime date = dateTime.Date;
1374
1375             for (int i = 0; i < adjustmentRules.Length; i++) {
1376                 if (adjustmentRules[i].DateStart <= date && adjustmentRules[i].DateEnd >= date) {
1377                     return adjustmentRules[i];
1378                 }
1379             }
1380
1381             return null;
1382         }
1383
1384         //
1385         // GetIsDaylightSavingsFromUtc -
1386         //
1387         // Helper function that checks if a given dateTime is in Daylight Saving Time (DST)
1388         // This function assumes the dateTime is in UTC and AdjustmentRule is in a different time zone
1389         //
1390         static private Boolean GetIsDaylightSavingsFromUtc(DateTime time, Int32 Year, TimeSpan utc, AdjustmentRule rule, out Boolean isAmbiguousLocalDst) {
1391             isAmbiguousLocalDst = false;
1392
1393             if (rule == null) {
1394                 return false;
1395             }
1396
1397             // Get the daylight changes for the year of the specified time.
1398             TimeSpan offset = utc; /* */
1399             DaylightTime daylightTime = GetDaylightTime(Year, rule);
1400
1401             // The start and end times represent the range of universal times that are in DST for that year.
1402             // Within that there is an ambiguous hour, usually right at the end, but at the beginning in
1403             // the unusual case of a negative daylight savings delta.
1404             DateTime startTime = daylightTime.Start - offset;
1405             DateTime endTime = daylightTime.End - offset - rule.DaylightDelta; /* */
1406             DateTime ambiguousStart;
1407             DateTime ambiguousEnd;
1408             if (daylightTime.Delta.Ticks > 0) {
1409                 ambiguousStart = endTime - daylightTime.Delta;
1410                 ambiguousEnd = endTime;
1411             } else {
1412                 ambiguousStart = startTime;
1413                 ambiguousEnd = startTime - daylightTime.Delta;
1414             }
1415
1416             Boolean isDst = CheckIsDst(startTime, time, endTime);
1417
1418             // See if the resulting local time becomes ambiguous. This must be captured here or the
1419             // DateTime will not be able to round-trip back to UTC accurately.
1420             if (isDst) {
1421                 isAmbiguousLocalDst = (time >= ambiguousStart && time < ambiguousEnd);
1422
1423                 if (!isAmbiguousLocalDst && ambiguousStart.Year != ambiguousEnd.Year) {
1424                     // there exists an extreme corner case where the start or end period is on a year boundary and
1425                     // because of this the comparison above might have been performed for a year-early or a year-later
1426                     // than it should have been.
1427                     DateTime ambiguousStartModified;
1428                     DateTime ambiguousEndModified;
1429                     try {
1430                         ambiguousStartModified = ambiguousStart.AddYears(1);
1431                         ambiguousEndModified   = ambiguousEnd.AddYears(1);
1432                         isAmbiguousLocalDst = (time >= ambiguousStart && time < ambiguousEnd);
1433                     }
1434                     catch (ArgumentOutOfRangeException) {}
1435
1436                     if (!isAmbiguousLocalDst) {
1437                         try {
1438                             ambiguousStartModified = ambiguousStart.AddYears(-1);
1439                             ambiguousEndModified   = ambiguousEnd.AddYears(-1);
1440                             isAmbiguousLocalDst = (time >= ambiguousStart && time < ambiguousEnd);
1441                         }
1442                         catch (ArgumentOutOfRangeException) {}
1443                     }
1444
1445                 }
1446             }
1447
1448             return isDst;
1449         }
1450
1451
1452         static private Boolean CheckIsDst(DateTime startTime, DateTime time, DateTime endTime) {
1453             Boolean isDst;
1454
1455             int startTimeYear = startTime.Year;
1456             int endTimeYear = endTime.Year;
1457
1458             if (startTimeYear != endTimeYear) {
1459                 endTime = endTime.AddYears(startTimeYear - endTimeYear);
1460             }
1461
1462             int timeYear = time.Year;
1463
1464             if (startTimeYear != timeYear) {
1465                 time = time.AddYears(startTimeYear - timeYear);
1466             }
1467
1468             if (startTime > endTime) {
1469                 // In southern hemisphere, the daylight saving time starts later in the year, and ends in the beginning of next year.
1470                 // Note, the summer in the southern hemisphere begins late in the year.
1471                 isDst = (time < endTime || time >= startTime);
1472             }
1473             else {
1474                 // In northern hemisphere, the daylight saving time starts in the middle of the year.
1475                 isDst = (time >= startTime && time < endTime);
1476             }
1477             return isDst;
1478         }
1479
1480         //
1481         // GetDaylightTime -
1482         //
1483         // Helper function that returns a DaylightTime from a year and AdjustmentRule
1484         //
1485         static private DaylightTime GetDaylightTime(Int32 year, AdjustmentRule rule) {
1486             TimeSpan delta = rule.DaylightDelta;
1487             DateTime startTime = TransitionTimeToDateTime(year, rule.DaylightTransitionStart);
1488             DateTime endTime = TransitionTimeToDateTime(year, rule.DaylightTransitionEnd);
1489             return new DaylightTime(startTime, endTime, delta);
1490         }
1491
1492         //
1493         // TransitionTimeToDateTime -
1494         //
1495         // Helper function that converts a year and TransitionTime into a DateTime
1496         //
1497         static private DateTime TransitionTimeToDateTime(Int32 year, TransitionTime transitionTime) {
1498             DateTime value;
1499             DateTime timeOfDay = transitionTime.TimeOfDay;
1500
1501             if (transitionTime.IsFixedDateRule) {
1502                 // create a DateTime from the passed in year and the properties on the transitionTime
1503
1504                 // if the day is out of range for the month then use the last day of the month
1505                 Int32 day = DateTime.DaysInMonth(year, transitionTime.Month);
1506
1507                 value = new DateTime(year, transitionTime.Month, (day < transitionTime.Day) ? day : transitionTime.Day,
1508                             timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
1509             }
1510             else {
1511                 if (transitionTime.Week <= 4) {
1512                     //
1513                     // Get the (transitionTime.Week)th Sunday.
1514                     //
1515                     value = new DateTime(year, transitionTime.Month, 1,
1516                             timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
1517
1518                     int dayOfWeek = (int)value.DayOfWeek;
1519                     int delta = (int)transitionTime.DayOfWeek - dayOfWeek;
1520                     if (delta < 0) {
1521                         delta += 7;
1522                     }
1523                     delta += 7 * (transitionTime.Week - 1);
1524
1525                     if (delta > 0) {
1526                         value = value.AddDays(delta);
1527                     }
1528                 }
1529                 else {
1530                     //
1531                     // If TransitionWeek is greater than 4, we will get the last week.
1532                     //
1533                     Int32 daysInMonth = DateTime.DaysInMonth(year, transitionTime.Month);
1534                     value = new DateTime(year, transitionTime.Month, daysInMonth,
1535                             timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
1536
1537                     // This is the day of week for the last day of the month.
1538                     int dayOfWeek = (int)value.DayOfWeek;
1539                     int delta = dayOfWeek - (int)transitionTime.DayOfWeek;
1540                     if (delta < 0) {
1541                         delta += 7;
1542                     }
1543
1544                     if (delta > 0) {
1545                         value = value.AddDays(-delta);
1546                     }
1547                 }
1548             }
1549             return value;
1550         }
1551
1552         //
1553         // IsInvalidTime -
1554         //
1555         // returns true when dateTime falls into a "hole in time".
1556         //
1557         public Boolean IsInvalidTime(DateTime dateTime) {
1558             Boolean isInvalid = false;
1559
1560             if ( (dateTime.Kind == DateTimeKind.Unspecified)
1561             ||   (dateTime.Kind == DateTimeKind.Local && this == Local) ) {
1562
1563                 // only check Unspecified and (Local when this TimeZoneInfo instance is Local)
1564                 AdjustmentRule rule = GetAdjustmentRuleForTime(dateTime);
1565
1566
1567                 if (rule != null) {
1568                     DaylightTime daylightTime = GetDaylightTime(dateTime.Year, rule);
1569                     isInvalid = GetIsInvalidTime(dateTime, rule, daylightTime);
1570                 }
1571                 else {
1572                     isInvalid = false;
1573                 }
1574             }
1575
1576             return isInvalid;
1577         }
1578
1579         //
1580         // GetIsInvalidTime -
1581         //
1582         // Helper function that checks if a given DateTime is in an invalid time ("time hole")
1583         // A "time hole" occurs at a DST transition point when time jumps forward;
1584         // For example, in Pacific Standard Time on Sunday, April 2, 2006 time jumps from
1585         // 1:59:59.9999999 to 3AM.  The time range 2AM to 2:59:59.9999999AM is the "time hole".
1586         // A "time hole" is not limited to only occurring at the start of DST, and may occur at
1587         // the end of DST as well.
1588         //
1589         static private Boolean GetIsInvalidTime(DateTime time, AdjustmentRule rule, DaylightTime daylightTime) {
1590             Boolean isInvalid = false;
1591             if (rule == null || rule.DaylightDelta == TimeSpan.Zero) {
1592                 return isInvalid;
1593             }
1594
1595             DateTime startInvalidTime;
1596             DateTime endInvalidTime;
1597
1598             // if at DST start we transition forward in time then there is an ambiguous time range at the DST end
1599             if (rule.DaylightDelta < TimeSpan.Zero) {
1600                 startInvalidTime = daylightTime.End;
1601                 endInvalidTime = daylightTime.End - rule.DaylightDelta; /* */
1602             }
1603             else {
1604                 startInvalidTime = daylightTime.Start;
1605                 endInvalidTime = daylightTime.Start + rule.DaylightDelta; /* */
1606             }
1607
1608             isInvalid = (time >= startInvalidTime && time < endInvalidTime);
1609
1610             if (!isInvalid && startInvalidTime.Year != endInvalidTime.Year) {
1611                 // there exists an extreme corner case where the start or end period is on a year boundary and
1612                 // because of this the comparison above might have been performed for a year-early or a year-later
1613                 // than it should have been.
1614                 DateTime startModifiedInvalidTime;
1615                 DateTime endModifiedInvalidTime;
1616                 try {
1617                     startModifiedInvalidTime = startInvalidTime.AddYears(1);
1618                     endModifiedInvalidTime   = endInvalidTime.AddYears(1);
1619                     isInvalid = (time >= startModifiedInvalidTime && time < endModifiedInvalidTime);
1620                 }
1621                 catch (ArgumentOutOfRangeException) {}
1622
1623                 if (!isInvalid) {
1624                     try {
1625                         startModifiedInvalidTime = startInvalidTime.AddYears(-1);
1626                         endModifiedInvalidTime  = endInvalidTime.AddYears(-1);
1627                         isInvalid = (time >= startModifiedInvalidTime && time < endModifiedInvalidTime);
1628                     }
1629                     catch (ArgumentOutOfRangeException) {}
1630                 }
1631             }
1632             return isInvalid;
1633         }
1634 #endregion
1635         }
1636
1637         struct TimeType {
1638                 public readonly int Offset;
1639                 public readonly bool IsDst;
1640                 public string Name;
1641
1642                 public TimeType (int offset, bool is_dst, string abbrev)
1643                 {
1644                         this.Offset = offset;
1645                         this.IsDst = is_dst;
1646                         this.Name = abbrev;
1647                 }
1648
1649                 public override string ToString ()
1650                 {
1651                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1652                 }
1653 #else
1654         }
1655 #endif
1656         }
1657 }