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.Runtime.InteropServices;
  37 using System.Text;
  38 using System.Globalization;
  39 using System.IO;
  40
  41 using Microsoft.Win32;
  42
  43 namespace System
  44 {
  45         partial class TimeZoneInfo
  46         {
  47                 TimeSpan baseUtcOffset;
  48                 public TimeSpan BaseUtcOffset {
  49                         get { return baseUtcOffset; }
  50                 }
  51
  52                 string daylightDisplayName;
  53                 public string DaylightName {
  54                         get {
  55                                 return supportsDaylightSavingTime
  56                                         ? daylightDisplayName
  57                                         : string.Empty;
  58                         }
  59                 }
  60
  61                 string displayName;
  62                 public string DisplayName {
  63                         get { return displayName; }
  64                 }
  65
  66                 string id;
  67                 public string Id {
  68                         get { return id; }
  69                 }
  70
  71                 static TimeZoneInfo local;
  72                 public static TimeZoneInfo Local {
  73                         get {
  74                                 var l = local;
  75                                 if (l == null) {
  76                                         l = CreateLocal ();
  77                                         if (l == null)
  78                                                 throw new TimeZoneNotFoundException ();
  79
  80                                         if (Interlocked.CompareExchange (ref local, l, null) != null)
  81                                                 l = local;
  82                                 }
  83
  84                                 return l;
  85                         }
  86                 }
  87
  88                 /*
  89                         TimeZone transitions are stored when there is a change on the base offset.
  90                 */
  91                 private List<KeyValuePair<DateTime, TimeType>> transitions;
  92
  93                 private static bool readlinkNotFound;
  94
  95                 [DllImport ("libc")]
  96                 private static extern int readlink (string path, byte[] buffer, int buflen);
  97
  98                 private static string readlink (string path)
  99                 {
 100                         if (readlinkNotFound)
 101                                 return null;
 102
 103                         byte[] buf = new byte [512];
 104                         int ret;
 105
 106                         try {
 107                                 ret = readlink (path, buf, buf.Length);
 108                         } catch (DllNotFoundException e) {
 109                                 readlinkNotFound = true;
 110                                 return null;
 111                         } catch (EntryPointNotFoundException e) {
 112                                 readlinkNotFound = true;
 113                                 return null;
 114                         }
 115
 116                         if (ret == -1) return null;
 117                         char[] cbuf = new char [512];
 118                         int chars = System.Text.Encoding.Default.GetChars (buf, 0, ret, cbuf, 0);
 119                         return new String (cbuf, 0, chars);
 120                 }
 121
 122                 private static bool TryGetNameFromPath (string path, out string name)
 123                 {
 124                         name = null;
 125                         var linkPath = readlink (path);
 126                         if (linkPath != null) {
 127                                 if (Path.IsPathRooted(linkPath))
 128                                         path = linkPath;
 129                                 else
 130                                         path = Path.Combine(Path.GetDirectoryName(path), linkPath);
 131                         }
 132
 133                         path = Path.GetFullPath (path);
 134
 135                         if (string.IsNullOrEmpty (TimeZoneDirectory))
 136                                 return false;
 137
 138                         var baseDir = TimeZoneDirectory;
 139                         if (baseDir [baseDir.Length-1] != Path.DirectorySeparatorChar)
 140                                 baseDir += Path.DirectorySeparatorChar;
 141
 142                         if (!path.StartsWith (baseDir, StringComparison.InvariantCulture))
 143                                 return false;
 144
 145                         name = path.Substring (baseDir.Length);
 146                         if (name == "localtime")
 147                                 name = "Local";
 148
 149                         return true;
 150                 }
 151
 152 #if !MOBILE || MOBILE_STATIC
 153                 static TimeZoneInfo CreateLocal ()
 154                 {
 155 #if !MOBILE_STATIC
 156                         if (IsWindows && LocalZoneKey != null) {
 157                                 string name = (string)LocalZoneKey.GetValue ("TimeZoneKeyName");
 158                                 if (name == null)
 159                                         name = (string)LocalZoneKey.GetValue ("StandardName"); // windows xp
 160                                 name = TrimSpecial (name);
 161                                 if (name != null)
 162                                         return TimeZoneInfo.FindSystemTimeZoneById (name);
 163                         }
 164 #endif
 165
 166                         var tz = Environment.GetEnvironmentVariable ("TZ");
 167                         if (tz != null) {
 168                                 if (tz == String.Empty)
 169                                         return Utc;
 170                                 try {
 171                                         return FindSystemTimeZoneByFileName (tz, Path.Combine (TimeZoneDirectory, tz));
 172                                 } catch {
 173                                         return Utc;
 174                                 }
 175                         }
 176
 177                         var tzFilePaths = new string [] {
 178                                 "/etc/localtime",
 179                                 Path.Combine (TimeZoneDirectory, "localtime")};
 180
 181                         foreach (var tzFilePath in tzFilePaths) {
 182                                 try {
 183                                         string tzName = null;
 184                                         if (!TryGetNameFromPath (tzFilePath, out tzName))
 185                                                 tzName = "Local";
 186                                         return FindSystemTimeZoneByFileName (tzName, tzFilePath);
 187                                 } catch (TimeZoneNotFoundException) {
 188                                         continue;
 189                                 }
 190                         }
 191
 192                         return Utc;
 193                 }
 194
 195                 static TimeZoneInfo FindSystemTimeZoneByIdCore (string id)
 196                 {
 197 #if LIBC
 198                         string filepath = Path.Combine (TimeZoneDirectory, id);
 199                         return FindSystemTimeZoneByFileName (id, filepath);
 200 #else
 201                         throw new NotImplementedException ();
 202 #endif
 203                 }
 204
 205                 static void GetSystemTimeZonesCore (List<TimeZoneInfo> systemTimeZones)
 206                 {
 207 #if !MOBILE_STATIC
 208                         if (TimeZoneKey != null) {
 209                                 foreach (string id in TimeZoneKey.GetSubKeyNames ()) {
 210                                         try {
 211                                                 systemTimeZones.Add (FindSystemTimeZoneById (id));
 212                                         } catch {}
 213                                 }
 214
 215                                 return;
 216                         }
 217 #endif
 218
 219 #if LIBC
 220                         string[] continents = new string [] {"Africa", "America", "Antarctica", "Arctic", "Asia", "Atlantic", "Australia", "Brazil", "Canada", "Chile", "Europe", "Indian", "Mexico", "Mideast", "Pacific", "US"};
 221                         foreach (string continent in continents) {
 222                                 try {
 223                                         foreach (string zonepath in Directory.GetFiles (Path.Combine (TimeZoneDirectory, continent))) {
 224                                                 try {
 225                                                         string id = String.Format ("{0}/{1}", continent, Path.GetFileName (zonepath));
 226                                                         systemTimeZones.Add (FindSystemTimeZoneById (id));
 227                                                 } catch (ArgumentNullException) {
 228                                                 } catch (TimeZoneNotFoundException) {
 229                                                 } catch (InvalidTimeZoneException) {
 230                                                 } catch (Exception) {
 231                                                         throw;
 232                                                 }
 233                                         }
 234                                 } catch {}
 235                         }
 236 #else
 237                         throw new NotImplementedException ("This method is not implemented for this platform");
 238 #endif
 239                 }
 240 #endif
 241
 242                 string standardDisplayName;
 243                 public string StandardName {
 244                         get { return standardDisplayName; }
 245                 }
 246
 247                 bool supportsDaylightSavingTime;
 248                 public bool SupportsDaylightSavingTime {
 249                         get  { return supportsDaylightSavingTime; }
 250                 }
 251
 252                 static TimeZoneInfo utc;
 253                 public static TimeZoneInfo Utc {
 254                         get {
 255                                 if (utc == null)
 256                                         utc = CreateCustomTimeZone ("UTC", new TimeSpan (0), "UTC", "UTC");
 257                                 return utc;
 258                         }
 259                 }
 260 #if LIBC
 261                 static string timeZoneDirectory;
 262                 static string TimeZoneDirectory {
 263                         get {
 264                                 if (timeZoneDirectory == null)
 265                                         timeZoneDirectory = "/usr/share/zoneinfo";
 266                                 return timeZoneDirectory;
 267                         }
 268                         set {
 269                                 ClearCachedData ();
 270                                 timeZoneDirectory = value;
 271                         }
 272                 }
 273 #endif
 274                 private AdjustmentRule [] adjustmentRules;
 275
 276 #if !MOBILE || MOBILE_STATIC
 277                 /// <summary>
 278                 /// Determine whether windows of not (taken Stephane Delcroix's code)
 279                 /// </summary>
 280                 private static bool IsWindows
 281                 {
 282                         get {
 283                                 int platform = (int) Environment.OSVersion.Platform;
 284                                 return ((platform != 4) && (platform != 6) && (platform != 128));
 285                         }
 286                 }
 287
 288                 /// <summary>
 289                 /// Needed to trim misc garbage in MS registry keys
 290                 /// </summary>
 291                 private static string TrimSpecial (string str)
 292                 {
 293                         if (str == null)
 294                                 return str;
 295                         var Istart = 0;
 296                         while (Istart < str.Length && !char.IsLetterOrDigit(str[Istart])) Istart++;
 297                         var Iend = str.Length - 1;
 298                         while (Iend > Istart && !char.IsLetterOrDigit(str[Iend]) && str[Iend] != ')') // zone name can include parentheses like "Central Standard Time (Mexico)"
 299                                 Iend--;
 300
 301                         return str.Substring (Istart, Iend-Istart+1);
 302                 }
 303
 304 #if !MOBILE_STATIC
 305                 static RegistryKey timeZoneKey;
 306                 static RegistryKey TimeZoneKey {
 307                         get {
 308                                 if (timeZoneKey != null)
 309                                         return timeZoneKey;
 310                                 if (!IsWindows)
 311                                         return null;
 312
 313                                 return timeZoneKey = Registry.LocalMachine.OpenSubKey (
 314                                         "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Time Zones",
 315                                         false);
 316                         }
 317                 }
 318
 319                 static RegistryKey localZoneKey;
 320                 static RegistryKey LocalZoneKey {
 321                         get {
 322                                 if (localZoneKey != null)
 323                                         return localZoneKey;
 324
 325                                 if (!IsWindows)
 326                                         return null;
 327
 328                                 return localZoneKey = Registry.LocalMachine.OpenSubKey (
 329                                         "SYSTEM\\CurrentControlSet\\Control\\TimeZoneInformation", false);
 330                         }
 331                 }
 332 #endif
 333 #endif
 334
 335                 private static bool TryAddTicks (DateTime date, long ticks, out DateTime result, DateTimeKind kind = DateTimeKind.Unspecified)
 336                 {
 337                         var resultTicks = date.Ticks + ticks;
 338                         if (resultTicks < DateTime.MinValue.Ticks) {
 339                                 result = DateTime.SpecifyKind (DateTime.MinValue, kind);
 340                                 return false;
 341                         }
 342
 343                         if (resultTicks > DateTime.MaxValue.Ticks) {
 344                                 result = DateTime.SpecifyKind (DateTime.MaxValue, kind);
 345                                 return false;
 346                         }
 347
 348                         result = new DateTime (resultTicks, kind);
 349                         return true;
 350                 }
 351
 352                 public static void ClearCachedData ()
 353                 {
 354                         local = null;
 355                         utc = null;
 356                         systemTimeZones = null;
 357                 }
 358
 359                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 360                 {
 361                         return ConvertTime (dateTime, dateTime.Kind == DateTimeKind.Utc ? TimeZoneInfo.Utc : TimeZoneInfo.Local, destinationTimeZone);
 362                 }
 363
 364                 public static DateTime ConvertTime (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)
 365                 {
 366                         if (sourceTimeZone == null)
 367                                 throw new ArgumentNullException ("sourceTimeZone");
 368
 369                         if (destinationTimeZone == null)
 370                                 throw new ArgumentNullException ("destinationTimeZone");
 371
 372                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 373                                 throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 374
 375                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 376                                 throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 377
 378                         if (sourceTimeZone.IsInvalidTime (dateTime))
 379                                 throw new ArgumentException ("dateTime parameter is an invalid time");
 380
 381                         if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone == TimeZoneInfo.Local && destinationTimeZone == TimeZoneInfo.Local)
 382                                 return dateTime;
 383
 384                         DateTime utc = ConvertTimeToUtc (dateTime, sourceTimeZone);
 385
 386                         if (destinationTimeZone != TimeZoneInfo.Utc) {
 387                                 utc = ConvertTimeFromUtc (utc, destinationTimeZone);
 388                                 if (dateTime.Kind == DateTimeKind.Unspecified)
 389                                         return DateTime.SpecifyKind (utc, DateTimeKind.Unspecified);
 390                         }
 391
 392                         return utc;
 393                 }
 394
 395                 public static DateTimeOffset ConvertTime(DateTimeOffset dateTimeOffset, TimeZoneInfo destinationTimeZone)
 396                 {
 397                         if (destinationTimeZone == null)
 398                                 throw new ArgumentNullException("destinationTimeZone");
 399
 400                         var utcDateTime = dateTimeOffset.UtcDateTime;
 401
 402                         bool isDst;
 403                         var utcOffset =  destinationTimeZone.GetUtcOffset(utcDateTime, out isDst);
 404
 405                         return new DateTimeOffset(DateTime.SpecifyKind(utcDateTime, DateTimeKind.Unspecified) + utcOffset, utcOffset);
 406                 }
 407
 408                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string destinationTimeZoneId)
 409                 {
 410                         return ConvertTime (dateTime, FindSystemTimeZoneById (destinationTimeZoneId));
 411                 }
 412
 413                 public static DateTime ConvertTimeBySystemTimeZoneId (DateTime dateTime, string sourceTimeZoneId, string destinationTimeZoneId)
 414                 {
 415                         TimeZoneInfo source_tz;
 416                         if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZoneId == TimeZoneInfo.Utc.Id) {
 417                                 source_tz = Utc;
 418                         } else {
 419                                 source_tz = FindSystemTimeZoneById (sourceTimeZoneId);
 420                         }
 421
 422                         return ConvertTime (dateTime, source_tz, FindSystemTimeZoneById (destinationTimeZoneId));
 423                 }
 424
 425                 public static DateTimeOffset ConvertTimeBySystemTimeZoneId (DateTimeOffset dateTimeOffset, string destinationTimeZoneId)
 426                 {
 427                         return ConvertTime (dateTimeOffset, FindSystemTimeZoneById (destinationTimeZoneId));
 428                 }
 429
 430                 private DateTime ConvertTimeFromUtc (DateTime dateTime)
 431                 {
 432                         if (dateTime.Kind == DateTimeKind.Local)
 433                                 throw new ArgumentException ("Kind property of dateTime is Local");
 434
 435                         if (this == TimeZoneInfo.Utc)
 436                                 return DateTime.SpecifyKind (dateTime, DateTimeKind.Utc);
 437
 438                         var utcOffset = GetUtcOffset (dateTime);
 439
 440                         var kind = (this == TimeZoneInfo.Local)? DateTimeKind.Local : DateTimeKind.Unspecified;
 441
 442                         DateTime result;
 443                         if (!TryAddTicks (dateTime, utcOffset.Ticks, out result, kind))
 444                                 return DateTime.SpecifyKind (DateTime.MaxValue, kind);
 445
 446                         return result;
 447                 }
 448
 449                 public static DateTime ConvertTimeFromUtc (DateTime dateTime, TimeZoneInfo destinationTimeZone)
 450                 {
 451                         if (destinationTimeZone == null)
 452                                 throw new ArgumentNullException ("destinationTimeZone");
 453
 454                         return destinationTimeZone.ConvertTimeFromUtc (dateTime);
 455                 }
 456
 457                 public static DateTime ConvertTimeToUtc (DateTime dateTime)
 458                 {
 459                         if (dateTime.Kind == DateTimeKind.Utc)
 460                                 return dateTime;
 461
 462                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local);
 463                 }
 464
 465                 static internal DateTime ConvertTimeToUtc(DateTime dateTime, TimeZoneInfoOptions flags)
 466                 {
 467                         return ConvertTimeToUtc (dateTime, TimeZoneInfo.Local, flags);
 468                 }
 469
 470                 public static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone)
 471                 {
 472                         return ConvertTimeToUtc (dateTime, sourceTimeZone, TimeZoneInfoOptions.None);
 473                 }
 474
 475                 static DateTime ConvertTimeToUtc (DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfoOptions flags)
 476                 {
 477                         if ((flags & TimeZoneInfoOptions.NoThrowOnInvalidTime) == 0) {
 478                                 if (sourceTimeZone == null)
 479                                         throw new ArgumentNullException ("sourceTimeZone");
 480
 481                                 if (dateTime.Kind == DateTimeKind.Utc && sourceTimeZone != TimeZoneInfo.Utc)
 482                                         throw new ArgumentException ("Kind property of dateTime is Utc but the sourceTimeZone does not equal TimeZoneInfo.Utc");
 483
 484                                 if (dateTime.Kind == DateTimeKind.Local && sourceTimeZone != TimeZoneInfo.Local)
 485                                         throw new ArgumentException ("Kind property of dateTime is Local but the sourceTimeZone does not equal TimeZoneInfo.Local");
 486
 487                                 if (sourceTimeZone.IsInvalidTime (dateTime))
 488                                         throw new ArgumentException ("dateTime parameter is an invalid time");
 489                         }
 490
 491                         if (dateTime.Kind == DateTimeKind.Utc)
 492                                 return dateTime;
 493
 494                         bool isDst;
 495                         var utcOffset = sourceTimeZone.GetUtcOffset (dateTime, out isDst);
 496
 497                         DateTime utcDateTime;
 498                         TryAddTicks (dateTime, -utcOffset.Ticks, out utcDateTime, DateTimeKind.Utc);
 499                         return utcDateTime;
 500                 }
 501
 502                 static internal TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out Boolean isAmbiguousLocalDst)
 503                 {
 504                         bool isDaylightSavings;
 505                         return GetUtcOffsetFromUtc(time, TimeZoneInfo.Local, out isDaylightSavings, out isAmbiguousLocalDst);
 506                 }
 507
 508                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName)
 509                 {
 510                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, null, null, true);
 511                 }
 512
 513                 public static TimeZoneInfo CreateCustomTimeZone (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules)
 514                 {
 515                         return CreateCustomTimeZone (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, false);
 516                 }
 517
 518                 public static TimeZoneInfo CreateCustomTimeZone ( string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
 519                 {
 520                         return new TimeZoneInfo (id, baseUtcOffset, displayName, standardDisplayName, daylightDisplayName, adjustmentRules, disableDaylightSavingTime);
 521                 }
 522
 523                 public override bool Equals (object obj)
 524                 {
 525                         return Equals (obj as TimeZoneInfo);
 526                 }
 527
 528                 public bool Equals (TimeZoneInfo other)
 529                 {
 530                         if (other == null)
 531                                 return false;
 532
 533                         return other.Id == this.Id && HasSameRules (other);
 534                 }
 535
 536                 public static TimeZoneInfo FindSystemTimeZoneById (string id)
 537                 {
 538                         //FIXME: this method should check for cached values in systemTimeZones
 539                         if (id == null)
 540                                 throw new ArgumentNullException ("id");
 541 #if !MOBILE
 542                         if (TimeZoneKey != null)
 543                         {
 544                                 if (id == "Coordinated Universal Time")
 545                                         id = "UTC"; //windows xp exception for "StandardName" property
 546                                 RegistryKey key = TimeZoneKey.OpenSubKey (id, false);
 547                                 if (key == null)
 548                                         throw new TimeZoneNotFoundException ();
 549                                 return FromRegistryKey(id, key);
 550                         }
 551 #endif
 552                         // Local requires special logic that already exists in the Local property (bug #326)
 553                         if (id == "Local")
 554                                 return Local;
 555
 556                         return FindSystemTimeZoneByIdCore (id);
 557                 }
 558
 559 #if LIBC
 560                 private static TimeZoneInfo FindSystemTimeZoneByFileName (string id, string filepath)
 561                 {
 562                         if (!File.Exists (filepath))
 563                                 throw new TimeZoneNotFoundException ();
 564
 565                         using (FileStream stream = File.OpenRead (filepath)) {
 566                                 return BuildFromStream (id, stream);
 567                         }
 568                 }
 569 #endif
 570
 571 #if !MOBILE
 572                 private static TimeZoneInfo FromRegistryKey (string id, RegistryKey key)
 573                 {
 574                         byte [] reg_tzi = (byte []) key.GetValue ("TZI");
 575
 576                         if (reg_tzi == null)
 577                                 throw new InvalidTimeZoneException ();
 578
 579                         int bias = BitConverter.ToInt32 (reg_tzi, 0);
 580                         TimeSpan baseUtcOffset = new TimeSpan (0, -bias, 0);
 581
 582                         string display_name = (string) key.GetValue ("Display");
 583                         string standard_name = (string) key.GetValue ("Std");
 584                         string daylight_name = (string) key.GetValue ("Dlt");
 585
 586                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
 587
 588                         RegistryKey dst_key = key.OpenSubKey ("Dynamic DST", false);
 589                         if (dst_key != null) {
 590                                 int first_year = (int) dst_key.GetValue ("FirstEntry");
 591                                 int last_year = (int) dst_key.GetValue ("LastEntry");
 592                                 int year;
 593
 594                                 for (year=first_year; year<=last_year; year++) {
 595                                         byte [] dst_tzi = (byte []) dst_key.GetValue (year.ToString ());
 596                                         if (dst_tzi != null) {
 597                                                 int start_year = year == first_year ? 1 : year;
 598                                                 int end_year = year == last_year ? 9999 : year;
 599                                                 ParseRegTzi(adjustmentRules, start_year, end_year, dst_tzi);
 600                                         }
 601                                 }
 602                         }
 603                         else
 604                                 ParseRegTzi(adjustmentRules, 1, 9999, reg_tzi);
 605
 606                         return CreateCustomTimeZone (id, baseUtcOffset, display_name, standard_name, daylight_name, ValidateRules (adjustmentRules).ToArray ());
 607                 }
 608
 609                 private static void ParseRegTzi (List<AdjustmentRule> adjustmentRules, int start_year, int end_year, byte [] buffer)
 610                 {
 611                         //int standard_bias = BitConverter.ToInt32 (buffer, 4); /* not sure how to handle this */
 612                         int daylight_bias = BitConverter.ToInt32 (buffer, 8);
 613
 614                         int standard_year = BitConverter.ToInt16 (buffer, 12);
 615                         int standard_month = BitConverter.ToInt16 (buffer, 14);
 616                         int standard_dayofweek = BitConverter.ToInt16 (buffer, 16);
 617                         int standard_day = BitConverter.ToInt16 (buffer, 18);
 618                         int standard_hour = BitConverter.ToInt16 (buffer, 20);
 619                         int standard_minute = BitConverter.ToInt16 (buffer, 22);
 620                         int standard_second = BitConverter.ToInt16 (buffer, 24);
 621                         int standard_millisecond = BitConverter.ToInt16 (buffer, 26);
 622
 623                         int daylight_year = BitConverter.ToInt16 (buffer, 28);
 624                         int daylight_month = BitConverter.ToInt16 (buffer, 30);
 625                         int daylight_dayofweek = BitConverter.ToInt16 (buffer, 32);
 626                         int daylight_day = BitConverter.ToInt16 (buffer, 34);
 627                         int daylight_hour = BitConverter.ToInt16 (buffer, 36);
 628                         int daylight_minute = BitConverter.ToInt16 (buffer, 38);
 629                         int daylight_second = BitConverter.ToInt16 (buffer, 40);
 630                         int daylight_millisecond = BitConverter.ToInt16 (buffer, 42);
 631
 632                         if (standard_month == 0 || daylight_month == 0)
 633                                 return;
 634
 635                         DateTime start_date;
 636                         DateTime start_timeofday = new DateTime (1, 1, 1, daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 637                         TransitionTime start_transition_time;
 638
 639                         if (daylight_year == 0) {
 640                                 start_date = new DateTime (start_year, 1, 1);
 641                                 start_transition_time = TransitionTime.CreateFloatingDateRule (
 642                                         start_timeofday, daylight_month, daylight_day,
 643                                         (DayOfWeek) daylight_dayofweek);
 644                         }
 645                         else {
 646                                 start_date = new DateTime (daylight_year, daylight_month, daylight_day,
 647                                         daylight_hour, daylight_minute, daylight_second, daylight_millisecond);
 648                                 start_transition_time = TransitionTime.CreateFixedDateRule (
 649                                         start_timeofday, daylight_month, daylight_day);
 650                         }
 651
 652                         DateTime end_date;
 653                         DateTime end_timeofday = new DateTime (1, 1, 1, standard_hour, standard_minute, standard_second, standard_millisecond);
 654                         TransitionTime end_transition_time;
 655
 656                         if (standard_year == 0) {
 657                                 end_date = new DateTime (end_year, 12, 31);
 658                                 end_transition_time = TransitionTime.CreateFloatingDateRule (
 659                                         end_timeofday, standard_month, standard_day,
 660                                         (DayOfWeek) standard_dayofweek);
 661                         }
 662                         else {
 663                                 end_date = new DateTime (standard_year, standard_month, standard_day,
 664                                         standard_hour, standard_minute, standard_second, standard_millisecond);
 665                                 end_transition_time = TransitionTime.CreateFixedDateRule (
 666                                         end_timeofday, standard_month, standard_day);
 667                         }
 668
 669                         TimeSpan daylight_delta = new TimeSpan(0, -daylight_bias, 0);
 670
 671                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (
 672                                 start_date, end_date, daylight_delta,
 673                                 start_transition_time, end_transition_time));
 674                 }
 675 #endif
 676
 677                 public AdjustmentRule [] GetAdjustmentRules ()
 678                 {
 679                         if (!supportsDaylightSavingTime || adjustmentRules == null)
 680                                 return new AdjustmentRule [0];
 681                         else
 682                                 return (AdjustmentRule []) adjustmentRules.Clone ();
 683                 }
 684
 685                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTime dateTime)
 686                 {
 687                         if (!IsAmbiguousTime (dateTime))
 688                                 throw new ArgumentException ("dateTime is not an ambiguous time");
 689
 690                         AdjustmentRule rule = GetApplicableRule (dateTime);
 691                         if (rule != null)
 692                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset + rule.DaylightDelta};
 693                         else
 694                                 return new TimeSpan[] {baseUtcOffset, baseUtcOffset};
 695                 }
 696
 697                 public TimeSpan [] GetAmbiguousTimeOffsets (DateTimeOffset dateTimeOffset)
 698                 {
 699                         if (!IsAmbiguousTime (dateTimeOffset))
 700                                 throw new ArgumentException ("dateTimeOffset is not an ambiguous time");
 701
 702                         throw new NotImplementedException ();
 703                 }
 704
 705                 public override int GetHashCode ()
 706                 {
 707                         int hash_code = Id.GetHashCode ();
 708                         foreach (AdjustmentRule rule in GetAdjustmentRules ())
 709                                 hash_code ^= rule.GetHashCode ();
 710                         return hash_code;
 711                 }
 712
 713                 void ISerializable.GetObjectData (SerializationInfo info, StreamingContext context)
 714                 {
 715                         if (info == null)
 716                                 throw new ArgumentNullException ("info");
 717                         info.AddValue ("Id", id);
 718                         info.AddValue ("DisplayName", displayName);
 719                         info.AddValue ("StandardName", standardDisplayName);
 720                         info.AddValue ("DaylightName", daylightDisplayName);
 721                         info.AddValue ("BaseUtcOffset", baseUtcOffset);
 722                         info.AddValue ("AdjustmentRules", adjustmentRules);
 723                         info.AddValue ("SupportsDaylightSavingTime", SupportsDaylightSavingTime);
 724                 }
 725
 726                 static ReadOnlyCollection<TimeZoneInfo> systemTimeZones;
 727
 728                 public static ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ()
 729                 {
 730                         if (systemTimeZones == null) {
 731                                 var tz = new List<TimeZoneInfo> ();
 732                                 GetSystemTimeZonesCore (tz);
 733                                 Interlocked.CompareExchange (ref systemTimeZones, new ReadOnlyCollection<TimeZoneInfo> (tz), null);
 734                         }
 735
 736                         return systemTimeZones;
 737                 }
 738
 739                 public TimeSpan GetUtcOffset (DateTime dateTime)
 740                 {
 741                         bool isDST;
 742                         return GetUtcOffset (dateTime, out isDST);
 743                 }
 744
 745                 public TimeSpan GetUtcOffset (DateTimeOffset dateTimeOffset)
 746                 {
 747                         bool isDST;
 748                         return GetUtcOffset (dateTimeOffset.UtcDateTime, out isDST);
 749                 }
 750
 751                 private TimeSpan GetUtcOffset (DateTime dateTime, out bool isDST)
 752                 {
 753                         isDST = false;
 754
 755                         TimeZoneInfo tz = this;
 756                         if (dateTime.Kind == DateTimeKind.Utc)
 757                                 tz = TimeZoneInfo.Utc;
 758
 759                         if (dateTime.Kind == DateTimeKind.Local)
 760                                 tz = TimeZoneInfo.Local;
 761
 762                         bool isTzDst;
 763                         var tzOffset = GetUtcOffsetHelper (dateTime, tz, out isTzDst);
 764
 765                         if (tz == this) {
 766                                 isDST = isTzDst;
 767                                 return tzOffset;
 768                         }
 769
 770                         DateTime utcDateTime;
 771                         if (!TryAddTicks (dateTime, -tzOffset.Ticks, out utcDateTime, DateTimeKind.Utc))
 772                                 return BaseUtcOffset;
 773
 774                         return GetUtcOffsetHelper (utcDateTime, this, out isDST);
 775                 }
 776
 777                 // This is an helper method used by the method above, do not use this on its own.
 778                 private static TimeSpan GetUtcOffsetHelper (DateTime dateTime, TimeZoneInfo tz, out bool isDST)
 779                 {
 780                         if (dateTime.Kind == DateTimeKind.Local && tz != TimeZoneInfo.Local)
 781                                 throw new Exception ();
 782
 783                         isDST = false;
 784
 785                         if (tz == TimeZoneInfo.Utc)
 786                                 return TimeSpan.Zero;
 787
 788                         TimeSpan offset;
 789                         if (tz.TryGetTransitionOffset(dateTime, out offset, out isDST))
 790                                 return offset;
 791
 792                         if (dateTime.Kind == DateTimeKind.Utc) {
 793                                 var utcRule = tz.GetApplicableRule (dateTime);
 794                                 if (utcRule != null && tz.IsInDST (utcRule, dateTime)) {
 795                                         isDST = true;
 796                                         return tz.BaseUtcOffset + utcRule.DaylightDelta;
 797                                 }
 798
 799                                 return tz.BaseUtcOffset;
 800                         }
 801
 802                         DateTime stdUtcDateTime;
 803                         if (!TryAddTicks (dateTime, -tz.BaseUtcOffset.Ticks, out stdUtcDateTime, DateTimeKind.Utc))
 804                                 return tz.BaseUtcOffset;
 805
 806                         var tzRule = tz.GetApplicableRule (stdUtcDateTime);
 807
 808                         DateTime dstUtcDateTime = DateTime.MinValue;
 809                         if (tzRule != null) {
 810                                 if (!TryAddTicks (stdUtcDateTime, -tzRule.DaylightDelta.Ticks, out dstUtcDateTime, DateTimeKind.Utc))
 811                                         return tz.BaseUtcOffset;
 812                         }
 813
 814                         if (tzRule != null && tz.IsInDST (tzRule, stdUtcDateTime) && tz.IsInDST (tzRule, dstUtcDateTime)) {
 815                                 isDST = true;
 816                                 return tz.BaseUtcOffset + tzRule.DaylightDelta;
 817                         }
 818
 819                         return tz.BaseUtcOffset;
 820                 }
 821
 822                 public bool HasSameRules (TimeZoneInfo other)
 823                 {
 824                         if (other == null)
 825                                 throw new ArgumentNullException ("other");
 826
 827                         if ((this.adjustmentRules == null) != (other.adjustmentRules == null))
 828                                 return false;
 829
 830                         if (this.adjustmentRules == null)
 831                                 return true;
 832
 833                         if (this.BaseUtcOffset != other.BaseUtcOffset)
 834                                 return false;
 835
 836                         if (this.adjustmentRules.Length != other.adjustmentRules.Length)
 837                                 return false;
 838
 839                         for (int i = 0; i < adjustmentRules.Length; i++) {
 840                                 if (! (this.adjustmentRules [i]).Equals (other.adjustmentRules [i]))
 841                                         return false;
 842                         }
 843
 844                         return true;
 845                 }
 846
 847                 public bool IsAmbiguousTime (DateTime dateTime)
 848                 {
 849                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 850                                 throw new ArgumentException ("Kind is Local and time is Invalid");
 851
 852                         if (this == TimeZoneInfo.Utc)
 853                                 return false;
 854
 855                         if (dateTime.Kind == DateTimeKind.Utc)
 856                                 dateTime = ConvertTimeFromUtc (dateTime);
 857
 858                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local)
 859                                 dateTime = ConvertTime (dateTime, TimeZoneInfo.Local, this);
 860
 861                         AdjustmentRule rule = GetApplicableRule (dateTime);
 862                         if (rule != null) {
 863                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionEnd, dateTime.Year);
 864                                 if (dateTime > tpoint - rule.DaylightDelta  && dateTime <= tpoint)
 865                                         return true;
 866                         }
 867
 868                         return false;
 869                 }
 870
 871                 public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset)
 872                 {
 873                         throw new NotImplementedException ();
 874                 }
 875
 876                 private bool IsInDST (AdjustmentRule rule, DateTime dateTime)
 877                 {
 878                         // Check whether we're in the dateTime year's DST period
 879                         if (IsInDSTForYear (rule, dateTime, dateTime.Year))
 880                                 return true;
 881
 882                         // We might be in the dateTime previous year's DST period
 883                         return dateTime.Year > 1 && IsInDSTForYear (rule, dateTime, dateTime.Year - 1);
 884                 }
 885
 886                 bool IsInDSTForYear (AdjustmentRule rule, DateTime dateTime, int year)
 887                 {
 888                         DateTime DST_start = TransitionPoint (rule.DaylightTransitionStart, year);
 889                         DateTime DST_end = TransitionPoint (rule.DaylightTransitionEnd, year + ((rule.DaylightTransitionStart.Month < rule.DaylightTransitionEnd.Month) ? 0 : 1));
 890                         if (dateTime.Kind == DateTimeKind.Utc) {
 891                                 DST_start -= BaseUtcOffset;
 892                                 DST_end -= (BaseUtcOffset + rule.DaylightDelta);
 893                         }
 894
 895                         return (dateTime >= DST_start && dateTime < DST_end);
 896                 }
 897
 898                 public bool IsDaylightSavingTime (DateTime dateTime)
 899                 {
 900                         if (dateTime.Kind == DateTimeKind.Local && IsInvalidTime (dateTime))
 901                                 throw new ArgumentException ("dateTime is invalid and Kind is Local");
 902
 903                         if (this == TimeZoneInfo.Utc)
 904                                 return false;
 905
 906                         if (!SupportsDaylightSavingTime)
 907                                 return false;
 908
 909                         bool isDst;
 910                         GetUtcOffset (dateTime, out isDst);
 911
 912                         return isDst;
 913                 }
 914
 915                 internal bool IsDaylightSavingTime (DateTime dateTime, TimeZoneInfoOptions flags)
 916                 {
 917                         return IsDaylightSavingTime (dateTime);
 918                 }
 919
 920                 public bool IsDaylightSavingTime (DateTimeOffset dateTimeOffset)
 921                 {
 922                         return IsDaylightSavingTime (dateTimeOffset.DateTime);
 923                 }
 924
 925                 internal DaylightTime GetDaylightChanges (int year)
 926                 {
 927                         DateTime start = DateTime.MinValue, end = DateTime.MinValue;
 928                         TimeSpan delta = new TimeSpan ();
 929
 930                         if (transitions != null) {
 931                                 end = DateTime.MaxValue;
 932                                 for (var i =  transitions.Count - 1; i >= 0; i--) {
 933                                         var pair = transitions [i];
 934                                         DateTime ttime = pair.Key;
 935                                         TimeType ttype = pair.Value;
 936
 937                                         if (ttime.Year > year)
 938                                                 continue;
 939                                         if (ttime.Year < year)
 940                                                 break;
 941
 942                                         if (ttype.IsDst) {
 943                                                 // DaylightTime.Delta is relative to the current BaseUtcOffset.
 944                                                 delta =  new TimeSpan (0, 0, ttype.Offset) - BaseUtcOffset;
 945                                                 start = ttime;
 946                                         } else {
 947                                                 end = ttime;
 948                                         }
 949                                 }
 950
 951                                 // DaylightTime.Start is relative to the Standard time.
 952                                 if (!TryAddTicks (start, BaseUtcOffset.Ticks, out start))
 953                                         start = DateTime.MinValue;
 954
 955                                 // DaylightTime.End is relative to the DST time.
 956                                 if (!TryAddTicks (end, BaseUtcOffset.Ticks + delta.Ticks, out end))
 957                                         end = DateTime.MinValue;
 958                         } else {
 959                                 AdjustmentRule first = null, last = null;
 960
 961                                 foreach (var rule in GetAdjustmentRules ()) {
 962                                         if (rule.DateStart.Year != year && rule.DateEnd.Year != year)
 963                                                 continue;
 964                                         if (rule.DateStart.Year == year)
 965                                                 first = rule;
 966                                         if (rule.DateEnd.Year == year)
 967                                                 last = rule;
 968                                 }
 969
 970                                 if (first == null || last == null)
 971                                         return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 972
 973                                 start = TransitionPoint (first.DaylightTransitionStart, year);
 974                                 end = TransitionPoint (last.DaylightTransitionEnd, year);
 975                                 delta = first.DaylightDelta;
 976                         }
 977
 978                         if (start == DateTime.MinValue || end == DateTime.MinValue)
 979                                 return new DaylightTime (new DateTime (), new DateTime (), new TimeSpan ());
 980
 981                         return new DaylightTime (start, end, delta);
 982                 }
 983
 984                 public bool IsInvalidTime (DateTime dateTime)
 985                 {
 986                         if (dateTime.Kind == DateTimeKind.Utc)
 987                                 return false;
 988                         if (dateTime.Kind == DateTimeKind.Local && this != Local)
 989                                 return false;
 990
 991                         AdjustmentRule rule = GetApplicableRule (dateTime);
 992                         if (rule != null) {
 993                                 DateTime tpoint = TransitionPoint (rule.DaylightTransitionStart, dateTime.Year);
 994                                 if (dateTime >= tpoint && dateTime < tpoint + rule.DaylightDelta)
 995                                         return true;
 996                         }
 997
 998                         return false;
 999                 }
1000
1001                 void IDeserializationCallback.OnDeserialization (object sender)
1002                 {
1003                         try {
1004                                         TimeZoneInfo.Validate (id, baseUtcOffset, adjustmentRules);
1005                                 } catch (ArgumentException ex) {
1006                                         throw new SerializationException ("invalid serialization data", ex);
1007                                 }
1008                 }
1009
1010                 private static void Validate (string id, TimeSpan baseUtcOffset, AdjustmentRule [] adjustmentRules)
1011                 {
1012                         if (id == null)
1013                                 throw new ArgumentNullException ("id");
1014
1015                         if (id == String.Empty)
1016                                 throw new ArgumentException ("id parameter is an empty string");
1017
1018                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
1019                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
1020
1021                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
1022                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
1023
1024 #if STRICT
1025                         if (id.Length > 32)
1026                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
1027 #endif
1028
1029                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
1030                                 AdjustmentRule prev = null;
1031                                 foreach (AdjustmentRule current in adjustmentRules) {
1032                                         if (current == null)
1033                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
1034
1035                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1036                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1037                                                 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;");
1038
1039                                         if (prev != null && prev.DateStart > current.DateStart)
1040                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1041
1042                                         if (prev != null && prev.DateEnd > current.DateStart)
1043                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1044
1045                                         if (prev != null && prev.DateEnd == current.DateStart)
1046                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1047
1048                                         prev = current;
1049                                 }
1050                         }
1051                 }
1052
1053                 public override string ToString ()
1054                 {
1055                         return DisplayName;
1056                 }
1057
1058                 private TimeZoneInfo (SerializationInfo info, StreamingContext context)
1059                 {
1060                         if (info == null)
1061                                 throw new ArgumentNullException ("info");
1062                         id = (string) info.GetValue ("Id", typeof (string));
1063                         displayName = (string) info.GetValue ("DisplayName", typeof (string));
1064                         standardDisplayName = (string) info.GetValue ("StandardName", typeof (string));
1065                         daylightDisplayName = (string) info.GetValue ("DaylightName", typeof (string));
1066                         baseUtcOffset = (TimeSpan) info.GetValue ("BaseUtcOffset", typeof (TimeSpan));
1067                         adjustmentRules = (TimeZoneInfo.AdjustmentRule []) info.GetValue ("AdjustmentRules", typeof (TimeZoneInfo.AdjustmentRule []));
1068                         supportsDaylightSavingTime = (bool) info.GetValue ("SupportsDaylightSavingTime", typeof (bool));
1069                 }
1070
1071                 private TimeZoneInfo (string id, TimeSpan baseUtcOffset, string displayName, string standardDisplayName, string daylightDisplayName, TimeZoneInfo.AdjustmentRule [] adjustmentRules, bool disableDaylightSavingTime)
1072                 {
1073                         if (id == null)
1074                                 throw new ArgumentNullException ("id");
1075
1076                         if (id == String.Empty)
1077                                 throw new ArgumentException ("id parameter is an empty string");
1078
1079                         if (baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
1080                                 throw new ArgumentException ("baseUtcOffset parameter does not represent a whole number of minutes");
1081
1082                         if (baseUtcOffset > new TimeSpan (14, 0, 0) || baseUtcOffset < new TimeSpan (-14, 0, 0))
1083                                 throw new ArgumentOutOfRangeException ("baseUtcOffset parameter is greater than 14 hours or less than -14 hours");
1084
1085 #if STRICT
1086                         if (id.Length > 32)
1087                                 throw new ArgumentException ("id parameter shouldn't be longer than 32 characters");
1088 #endif
1089
1090                         bool supportsDaylightSavingTime = !disableDaylightSavingTime;
1091
1092                         if (adjustmentRules != null && adjustmentRules.Length != 0) {
1093                                 AdjustmentRule prev = null;
1094                                 foreach (AdjustmentRule current in adjustmentRules) {
1095                                         if (current == null)
1096                                                 throw new InvalidTimeZoneException ("one or more elements in adjustmentRules are null");
1097
1098                                         if ((baseUtcOffset + current.DaylightDelta < new TimeSpan (-14, 0, 0)) ||
1099                                                         (baseUtcOffset + current.DaylightDelta > new TimeSpan (14, 0, 0)))
1100                                                 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;");
1101
1102                                         if (prev != null && prev.DateStart > current.DateStart)
1103                                                 throw new InvalidTimeZoneException ("adjustment rules specified in adjustmentRules parameter are not in chronological order");
1104
1105                                         if (prev != null && prev.DateEnd > current.DateStart)
1106                                                 throw new InvalidTimeZoneException ("some adjustment rules in the adjustmentRules parameter overlap");
1107
1108                                         if (prev != null && prev.DateEnd == current.DateStart)
1109                                                 throw new InvalidTimeZoneException ("a date can have multiple adjustment rules applied to it");
1110
1111                                         prev = current;
1112                                 }
1113                         } else {
1114                                 supportsDaylightSavingTime = false;
1115                         }
1116
1117                         this.id = id;
1118                         this.baseUtcOffset = baseUtcOffset;
1119                         this.displayName = displayName ?? id;
1120                         this.standardDisplayName = standardDisplayName ?? id;
1121                         this.daylightDisplayName = daylightDisplayName;
1122                         this.supportsDaylightSavingTime = supportsDaylightSavingTime;
1123                         this.adjustmentRules = adjustmentRules;
1124                 }
1125
1126                 private AdjustmentRule GetApplicableRule (DateTime dateTime)
1127                 {
1128                         //Applicable rules are in standard time
1129                         DateTime date = dateTime;
1130
1131                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1132                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date))
1133                                         return null;
1134                         } else if (dateTime.Kind == DateTimeKind.Utc && this != TimeZoneInfo.Utc) {
1135                                 if (!TryAddTicks (date, BaseUtcOffset.Ticks, out date))
1136                                         return null;
1137                         }
1138
1139                         // get the date component of the datetime
1140                         date = date.Date;
1141
1142                         if (adjustmentRules != null) {
1143                                 foreach (AdjustmentRule rule in adjustmentRules) {
1144                                         if (rule.DateStart > date)
1145                                                 return null;
1146                                         if (rule.DateEnd < date)
1147                                                 continue;
1148                                         return rule;
1149                                 }
1150                         }
1151                         return null;
1152                 }
1153
1154                 private bool TryGetTransitionOffset (DateTime dateTime, out TimeSpan offset,out bool isDst)
1155                 {
1156                         offset = BaseUtcOffset;
1157                         isDst = false;
1158
1159                         if (transitions == null)
1160                                 return false;
1161
1162                         //Transitions are in UTC
1163                         DateTime date = dateTime;
1164
1165                         if (dateTime.Kind == DateTimeKind.Local && this != TimeZoneInfo.Local) {
1166                                 if (!TryAddTicks (date.ToUniversalTime (), BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1167                                         return false;
1168                         }
1169
1170                         if (dateTime.Kind != DateTimeKind.Utc) {
1171                                 if (!TryAddTicks (date, -BaseUtcOffset.Ticks, out date, DateTimeKind.Utc))
1172                                         return false;
1173                         }
1174
1175                         for (var i =  transitions.Count - 1; i >= 0; i--) {
1176                                 var pair = transitions [i];
1177                                 DateTime ttime = pair.Key;
1178                                 TimeType ttype = pair.Value;
1179
1180                                 if (ttime > date)
1181                                         continue;
1182
1183                                 offset =  new TimeSpan (0, 0, ttype.Offset);
1184                                 isDst = ttype.IsDst;
1185
1186                                 return true;
1187                         }
1188
1189                         return false;
1190                 }
1191
1192                 private static DateTime TransitionPoint (TransitionTime transition, int year)
1193                 {
1194                         if (transition.IsFixedDateRule)
1195                                 return new DateTime (year, transition.Month, transition.Day) + transition.TimeOfDay.TimeOfDay;
1196
1197                         DayOfWeek first = (new DateTime (year, transition.Month, 1)).DayOfWeek;
1198                         int day = 1 + (transition.Week - 1) * 7 + (transition.DayOfWeek - first + 7) % 7;
1199                         if (day >  DateTime.DaysInMonth (year, transition.Month))
1200                                 day -= 7;
1201                         if (day < 1)
1202                                 day += 7;
1203                         return new DateTime (year, transition.Month, day) + transition.TimeOfDay.TimeOfDay;
1204                 }
1205
1206                 static List<AdjustmentRule> ValidateRules (List<AdjustmentRule> adjustmentRules)
1207                 {
1208                         AdjustmentRule prev = null;
1209                         foreach (AdjustmentRule current in adjustmentRules.ToArray ()) {
1210                                 if (prev != null && prev.DateEnd > current.DateStart) {
1211                                         adjustmentRules.Remove (current);
1212                                 }
1213                                 prev = current;
1214                         }
1215                         return adjustmentRules;
1216                 }
1217
1218 #if LIBC || MONOTOUCH
1219                 const int BUFFER_SIZE = 16384; //Big enough for any tz file (on Oct 2008, all tz files are under 10k)
1220
1221                 private static TimeZoneInfo BuildFromStream (string id, Stream stream)
1222                 {
1223                         byte [] buffer = new byte [BUFFER_SIZE];
1224                         int length = stream.Read (buffer, 0, BUFFER_SIZE);
1225
1226                         if (!ValidTZFile (buffer, length))
1227                                 throw new InvalidTimeZoneException ("TZ file too big for the buffer");
1228
1229                         try {
1230                                 return ParseTZBuffer (id, buffer, length);
1231                         } catch (InvalidTimeZoneException) {
1232                                 throw;
1233                         } catch (Exception e) {
1234                                 throw new InvalidTimeZoneException ("Time zone information file contains invalid data", e);
1235                         }
1236                 }
1237
1238                 private static bool ValidTZFile (byte [] buffer, int length)
1239                 {
1240                         StringBuilder magic = new StringBuilder ();
1241
1242                         for (int i = 0; i < 4; i++)
1243                                 magic.Append ((char)buffer [i]);
1244
1245                         if (magic.ToString () != "TZif")
1246                                 return false;
1247
1248                         if (length >= BUFFER_SIZE)
1249                                 return false;
1250
1251                         return true;
1252                 }
1253
1254                 static int SwapInt32 (int i)
1255                 {
1256                         return (((i >> 24) & 0xff)
1257                                 | ((i >> 8) & 0xff00)
1258                                 | ((i << 8) & 0xff0000)
1259                                 | (((i & 0xff) << 24)));
1260                 }
1261
1262                 static int ReadBigEndianInt32 (byte [] buffer, int start)
1263                 {
1264                         int i = BitConverter.ToInt32 (buffer, start);
1265                         if (!BitConverter.IsLittleEndian)
1266                                 return i;
1267
1268                         return SwapInt32 (i);
1269                 }
1270
1271                 private static TimeZoneInfo ParseTZBuffer (string id, byte [] buffer, int length)
1272                 {
1273                         //Reading the header. 4 bytes for magic, 16 are reserved
1274                         int ttisgmtcnt = ReadBigEndianInt32 (buffer, 20);
1275                         int ttisstdcnt = ReadBigEndianInt32 (buffer, 24);
1276                         int leapcnt = ReadBigEndianInt32 (buffer, 28);
1277                         int timecnt = ReadBigEndianInt32 (buffer, 32);
1278                         int typecnt = ReadBigEndianInt32 (buffer, 36);
1279                         int charcnt = ReadBigEndianInt32 (buffer, 40);
1280
1281                         if (length < 44 + timecnt * 5 + typecnt * 6 + charcnt + leapcnt * 8 + ttisstdcnt + ttisgmtcnt)
1282                                 throw new InvalidTimeZoneException ();
1283
1284                         Dictionary<int, string> abbreviations = ParseAbbreviations (buffer, 44 + 4 * timecnt + timecnt + 6 * typecnt, charcnt);
1285                         Dictionary<int, TimeType> time_types = ParseTimesTypes (buffer, 44 + 4 * timecnt + timecnt, typecnt, abbreviations);
1286                         List<KeyValuePair<DateTime, TimeType>> transitions = ParseTransitions (buffer, 44, timecnt, time_types);
1287
1288                         if (time_types.Count == 0)
1289                                 throw new InvalidTimeZoneException ();
1290
1291                         if (time_types.Count == 1 && time_types[0].IsDst)
1292                                 throw new InvalidTimeZoneException ();
1293
1294                         TimeSpan baseUtcOffset = new TimeSpan (0);
1295                         TimeSpan dstDelta = new TimeSpan (0);
1296                         string standardDisplayName = null;
1297                         string daylightDisplayName = null;
1298                         bool dst_observed = false;
1299                         DateTime dst_start = DateTime.MinValue;
1300                         List<AdjustmentRule> adjustmentRules = new List<AdjustmentRule> ();
1301                         bool storeTransition = false;
1302
1303                         for (int i = 0; i < transitions.Count; i++) {
1304                                 var pair = transitions [i];
1305                                 DateTime ttime = pair.Key;
1306                                 TimeType ttype = pair.Value;
1307                                 if (!ttype.IsDst) {
1308                                         if (standardDisplayName != ttype.Name)
1309                                                 standardDisplayName = ttype.Name;
1310                                         if (baseUtcOffset.TotalSeconds != ttype.Offset) {
1311                                                 baseUtcOffset = new TimeSpan (0, 0, ttype.Offset);
1312                                                 if (adjustmentRules.Count > 0) // We ignore AdjustmentRules but store transitions.
1313                                                         storeTransition = true;
1314                                                 adjustmentRules = new List<AdjustmentRule> ();
1315                                                 dst_observed = false;
1316                                         }
1317                                         if (dst_observed) {
1318                                                 //FIXME: check additional fields for this:
1319                                                 //most of the transitions are expressed in GMT
1320                                                 dst_start += baseUtcOffset;
1321                                                 DateTime dst_end = ttime + baseUtcOffset + dstDelta;
1322
1323                                                 //some weird timezone (America/Phoenix) have end dates on Jan 1st
1324                                                 if (dst_end.Date == new DateTime (dst_end.Year, 1, 1) && dst_end.Year > dst_start.Year)
1325                                                         dst_end -= new TimeSpan (24, 0, 0);
1326
1327                                                 /*
1328                                                  * AdjustmentRule specifies a DST period that starts and ends within a year.
1329                                                  * When we have a DST period longer than a year, the generated AdjustmentRule may not be usable.
1330                                                  * Thus we fallback to the transitions.
1331                                                  */
1332                                                 if (dst_start.AddYears (1) < dst_end)
1333                                                         storeTransition = true;
1334
1335                                                 DateTime dateStart, dateEnd;
1336                                                 if (dst_start.Month < 7)
1337                                                         dateStart = new DateTime (dst_start.Year, 1, 1);
1338                                                 else
1339                                                         dateStart = new DateTime (dst_start.Year, 7, 1);
1340
1341                                                 if (dst_end.Month >= 7)
1342                                                         dateEnd = new DateTime (dst_end.Year, 12, 31);
1343                                                 else
1344                                                         dateEnd = new DateTime (dst_end.Year, 6, 30);
1345
1346
1347                                                 TransitionTime transition_start = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_start.TimeOfDay, dst_start.Month, dst_start.Day);
1348                                                 TransitionTime transition_end = TransitionTime.CreateFixedDateRule (new DateTime (1, 1, 1) + dst_end.TimeOfDay, dst_end.Month, dst_end.Day);
1349                                                 if  (transition_start != transition_end) //y, that happened in Argentina in 1943-1946
1350                                                         adjustmentRules.Add (AdjustmentRule.CreateAdjustmentRule (dateStart, dateEnd, dstDelta, transition_start, transition_end));
1351                                         }
1352                                         dst_observed = false;
1353                                 } else {
1354                                         if (daylightDisplayName != ttype.Name)
1355                                                 daylightDisplayName = ttype.Name;
1356                                         if (dstDelta.TotalSeconds != ttype.Offset - baseUtcOffset.TotalSeconds) {
1357                                                 // Round to nearest minute, since it's not possible to create an adjustment rule
1358                                                 // with sub-minute precision ("The TimeSpan parameter cannot be specified more precisely than whole minutes.")
1359                                                 // This happens for instance with Europe/Dublin, which had an offset of 34 minutes and 39 seconds in 1916.
1360                                                 dstDelta = new TimeSpan (0, 0, ttype.Offset) - baseUtcOffset;
1361                                                 if (dstDelta.Ticks % TimeSpan.TicksPerMinute != 0)
1362                                                         dstDelta = TimeSpan.FromMinutes ((long) (dstDelta.TotalMinutes + 0.5f));
1363                                         }
1364
1365                                         dst_start = ttime;
1366                                         dst_observed = true;
1367                                 }
1368                         }
1369
1370                         TimeZoneInfo tz;
1371                         if (adjustmentRules.Count == 0 && !storeTransition) {
1372                                 if (standardDisplayName == null) {
1373                                         var t = time_types [0];
1374                                         standardDisplayName = t.Name;
1375                                         baseUtcOffset = new TimeSpan (0, 0, t.Offset);
1376                                 }
1377                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName);
1378                         } else {
1379                                 tz = CreateCustomTimeZone (id, baseUtcOffset, id, standardDisplayName, daylightDisplayName, ValidateRules (adjustmentRules).ToArray ());
1380                         }
1381
1382                         if (storeTransition && transitions.Count > 0) {
1383                                 tz.transitions = transitions;
1384                                 tz.supportsDaylightSavingTime = true;
1385                         }
1386
1387                         return tz;
1388                 }
1389
1390                 static Dictionary<int, string> ParseAbbreviations (byte [] buffer, int index, int count)
1391                 {
1392                         var abbrevs = new Dictionary<int, string> ();
1393                         int abbrev_index = 0;
1394                         var sb = new StringBuilder ();
1395                         for (int i = 0; i < count; i++) {
1396                                 char c = (char) buffer [index + i];
1397                                 if (c != '\0')
1398                                         sb.Append (c);
1399                                 else {
1400                                         abbrevs.Add (abbrev_index, sb.ToString ());
1401                                         //Adding all the substrings too, as it seems to be used, at least for Africa/Windhoek
1402                                         //j == sb.Length empty substring also needs to be added #31432
1403                                         for (int j = 1; j <= sb.Length; j++)
1404                                                 abbrevs.Add (abbrev_index + j, sb.ToString (j, sb.Length - j));
1405                                         abbrev_index = i + 1;
1406                                         sb = new StringBuilder ();
1407                                 }
1408                         }
1409                         return abbrevs;
1410                 }
1411
1412                 static Dictionary<int, TimeType> ParseTimesTypes (byte [] buffer, int index, int count, Dictionary<int, string> abbreviations)
1413                 {
1414                         var types = new Dictionary<int, TimeType> (count);
1415                         for (int i = 0; i < count; i++) {
1416                                 int offset = ReadBigEndianInt32 (buffer, index + 6 * i);
1417
1418                                 //
1419                                 // The official tz database contains timezone with GMT offsets
1420                                 // not only in whole hours/minutes but in seconds. This happens for years
1421                                 // before 1901. For example
1422                                 //
1423                                 // NAME                 GMTOFF   RULES  FORMAT  UNTIL
1424                                 // Europe/Madrid        -0:14:44 -      LMT     1901 Jan  1  0:00s
1425                                 //
1426                                 // .NET as of 4.6.2 cannot handle that and uses hours/minutes only, so
1427                                 // we remove seconds to not crash later
1428                                 //
1429                                 offset = (offset / 60) * 60;
1430
1431                                 byte is_dst = buffer [index + 6 * i + 4];
1432                                 byte abbrev = buffer [index + 6 * i + 5];
1433                                 types.Add (i, new TimeType (offset, (is_dst != 0), abbreviations [(int)abbrev]));
1434                         }
1435                         return types;
1436                 }
1437
1438                 static List<KeyValuePair<DateTime, TimeType>> ParseTransitions (byte [] buffer, int index, int count, Dictionary<int, TimeType> time_types)
1439                 {
1440                         var list = new List<KeyValuePair<DateTime, TimeType>> (count);
1441                         for (int i = 0; i < count; i++) {
1442                                 int unixtime = ReadBigEndianInt32 (buffer, index + 4 * i);
1443                                 DateTime ttime = DateTimeFromUnixTime (unixtime);
1444                                 byte ttype = buffer [index + 4 * count + i];
1445                                 list.Add (new KeyValuePair<DateTime, TimeType> (ttime, time_types [(int)ttype]));
1446                         }
1447                         return list;
1448                 }
1449
1450                 static DateTime DateTimeFromUnixTime (long unix_time)
1451                 {
1452                         DateTime date_time = new DateTime (1970, 1, 1);
1453                         return date_time.AddSeconds (unix_time);
1454                 }
1455
1456 #region reference sources
1457                 // Shortcut for TimeZoneInfo.Local.GetUtcOffset
1458                 internal static TimeSpan GetLocalUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1459                 {
1460                         bool dst;
1461                         return Local.GetUtcOffset (dateTime, out dst);
1462                 }
1463
1464                 internal TimeSpan GetUtcOffset(DateTime dateTime, TimeZoneInfoOptions flags)
1465                 {
1466                         bool dst;
1467                         return GetUtcOffset (dateTime, out dst);
1468                 }
1469
1470                 static internal TimeSpan GetUtcOffsetFromUtc (DateTime time, TimeZoneInfo zone, out Boolean isDaylightSavings, out Boolean isAmbiguousLocalDst)
1471                 {
1472                         isDaylightSavings = false;
1473                         isAmbiguousLocalDst = false;
1474                         TimeSpan baseOffset = zone.BaseUtcOffset;
1475
1476                         if (zone.IsAmbiguousTime (time)) {
1477                                 isAmbiguousLocalDst = true;
1478                                 return baseOffset;
1479                         }
1480
1481                         return zone.GetUtcOffset (time, out isDaylightSavings);
1482                 }
1483 #endregion
1484         }
1485
1486         class TimeType {
1487                 public readonly int Offset;
1488                 public readonly bool IsDst;
1489                 public string Name;
1490
1491                 public TimeType (int offset, bool is_dst, string abbrev)
1492                 {
1493                         this.Offset = offset;
1494                         this.IsDst = is_dst;
1495                         this.Name = abbrev;
1496                 }
1497
1498                 public override string ToString ()
1499                 {
1500                         return "offset: " + Offset + "s, is_dst: " + IsDst + ", zone name: " + Name;
1501                 }
1502 #else
1503         }
1504 #endif
1505         }
1506 }