class/corlib/System.Globalization/PersianCalendar.cs

   1 //
   2 // System.Globalization.PersianCalendar.cs
   3 //
   4 // Authors:
   5 //   Roozbeh Pournader (roozbeh@farsiweb.info)
   6 //   Ulrich Kunitz
   7 //
   8 // Copyright (C) 2002 Ulrich Kunitz
   9 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
  10 // Copyright (C) 2005 Sharif FarsiWeb, Inc. (http://www.farsiweb.info)
  11 //
  12 // Permission is hereby granted, free of charge, to any person obtaining
  13 // a copy of this software and associated documentation files (the
  14 // "Software"), to deal in the Software without restriction, including
  15 // without limitation the rights to use, copy, modify, merge, publish,
  16 // distribute, sublicense, and/or sell copies of the Software, and to
  17 // permit persons to whom the Software is furnished to do so, subject to
  18 // the following conditions:
  19 //
  20 // The above copyright notice and this permission notice shall be
  21 // included in all copies or substantial portions of the Software.
  22 //
  23 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  24 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  25 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  26 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  27 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  28 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  29 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  30 //
  31
  32 namespace System.Globalization {
  33
  34 using System;
  35 using System.IO;
  36 using System.Runtime.InteropServices;
  37
  38 /// <summary>
  39 /// This is the Persian calendar of Iran, also known as the Iranian
  40 /// calendar or the Jalaali calendar. The Afghan calendar may or may
  41 /// not be different, as different sources disagree about it.
  42 /// </summary>
  43 /// <remarks>
  44 /// <para>The implemented algorithm is the simple 33-year arithmetic
  45 /// calendar, which is not the same as the official Iranian calendar.
  46 /// But this arithmetic calendar has been confirmed to produce the
  47 /// same results as the official Iranian calendar at least
  48 /// from 1925 C.E., when the calendar was officially introduced,
  49 /// to 2088 C.E. This is the same algorithm that is used in .NET.
  50 /// </para>
  51 /// <para>The Iranian law explicitly mentions that the true solar year
  52 /// should be used, which requires astronomical calculations of the
  53 /// March equinox and the solar apparent noon. The exact locale for
  54 /// observation of the apparent noon is not mentioned in the 1925 law,
  55 /// but the current practice is using the 52.5 E meridian, which is
  56 /// the meridian defining the official timezone of Iran.
  57 /// </para>
  58 /// <para>Also, please note that implementing the Persian calendar
  59 /// using the 2820-year arithmetic algorithm, as suggested by
  60 /// Ahmad Birashk and others, is less accurate than the 33-year
  61 /// calendar: first, it fails earlier than the 33-year cycle in
  62 /// matching the official astronomical calendar (first failure is
  63 /// in 2025 C.E.), and second, the 2820-year suggested rule is based
  64 /// on the mean tropical year, not the mean March equinoctial year.
  65 /// </para>
  66 /// </remarks>
  67 [Serializable]
  68 public class PersianCalendar : Calendar {
  69         /// <summary>
  70         /// Constructor.
  71         /// </summary>
  72         public PersianCalendar() {
  73                 M_AbbrEraNames = new string[] {"A.P."};
  74                 M_EraNames = new string[] {"Anno Persico"};
  75                 if (twoDigitYearMax == 99)
  76                         // FIXME: the .NET documentation does not mention the default value,
  77                         // This is the value mentioned in the .NET documentation example result.
  78                         twoDigitYearMax = 1410;
  79         }
  80
  81         /// <summary>
  82         /// The era number for the Anno Persico (A.P.) era, called
  83         /// plain PersianEra.
  84         /// </summary>
  85         public static readonly int PersianEra = 1;
  86
  87         /// <summary>
  88         /// The
  89         /// <see cref="T:System.DateTime"/> ticks for first day of
  90         /// year 1 A.P.
  91         /// </summary>
  92         internal const long M_MinTicks = 196036416000000000L;
  93
  94         /// <summary>
  95         /// The minimum year in the A.P. era supported.
  96         /// </summary>
  97         internal const int M_MinYear = 1;
  98
  99         /// <value>Overridden. Gives the eras supported by the Persian
 100         /// calendar as an array of integers.
 101         /// </value>
 102         public override int[] Eras {
 103                 get {
 104                         return new int[] { PersianEra };
 105                 }
 106         }
 107
 108         public override int TwoDigitYearMax {
 109                 get {
 110                         return twoDigitYearMax;
 111                 }
 112                 set {
 113                         CheckReadOnly ();
 114                         M_ArgumentInRange ("value", value, 100, M_MaxYear);
 115
 116                         twoDigitYearMax = value;
 117                 }
 118         }
 119
 120         /// <summary>
 121         /// A protected member checking a
 122         /// <see cref="T:System.DateTime"/> value.
 123         /// </summary>
 124         /// <param name="time">The
 125         /// <see cref="T:System.DateTime"/>
 126         /// to check.
 127         /// </param>
 128         /// <exception cref="T:System.ArgumentOutOfRangeException">
 129         /// The exception is thrown if the
 130         /// <see cref="T:System.DateTime"/> parameter is before the
 131         /// year 1 A.P.
 132         /// </exception>
 133         internal void M_CheckDateTime(DateTime time)
 134         {
 135                 if (time.Ticks < M_MinTicks)
 136                         throw new ArgumentOutOfRangeException(
 137                                 "time",
 138                                 "Only positive Persian years are supported.");
 139         }
 140
 141         /// <summary>
 142         /// A protected method checking the era number.
 143         /// </summary>
 144         /// <param name="era">The era number.</param>
 145         /// <exception name="T:System.ArgumentException">
 146         /// The exception is thrown if the era is not equal
 147         /// <see cref="F:PersianEra"/>.
 148         /// </exception>
 149         internal void M_CheckEra(ref int era)
 150         {
 151                 if (era == CurrentEra)
 152                         era = PersianEra;
 153                 if (era != PersianEra)
 154                         throw new ArgumentException("Era value was not valid.");
 155         }
 156
 157         /// <summary>
 158         /// A protected method checking calendar year and the era number.
 159         /// </summary>
 160         /// <param name="year">An integer representing the calendar year.
 161         /// </param>
 162         /// <param name="era">The era number.</param>
 163         /// <exception cref="T:System.ArgumentException">
 164         /// The exception is thrown if the era is not equal
 165         /// <see cref="F:PersianEra"/>.
 166         /// </exception>
 167         /// <exception cref="T:System.ArgumentOutOfRangeException">
 168         /// The exception is thrown if the calendar year is outside of
 169         /// the allowed range.
 170         /// </exception>
 171         internal override void M_CheckYE(int year, ref int era)
 172         {
 173                 M_CheckEra(ref era);
 174                 if (year < M_MinYear || year > M_MaxYear)
 175                         throw new ArgumentOutOfRangeException(
 176                                 "year",
 177                                 "Only Persian years between 1 and 9378," +
 178                                 " inclusive, are supported.");
 179         }
 180
 181         /// <summary>
 182         /// A protected method checking the calendar year, month, and
 183         /// era number.
 184         /// </summary>
 185         /// <param name="year">An integer representing the calendar year.
 186         /// </param>
 187         /// <param name="month">An integer giving the calendar month.
 188         /// </param>
 189         /// <param name="era">The era number.</param>
 190         /// <exception cref="T:System.ArgumentException">
 191         /// The exception is thrown if the era is not equal
 192         /// <see cref="F:PersianEra"/>.
 193         /// </exception>
 194         /// <exception cref="T:System.ArgumentOutOfRangeException">
 195         /// The exception is thrown if the calendar year or month is
 196         /// outside of the allowed range.
 197         /// </exception>
 198         internal void M_CheckYME(int year, int month, ref int era)
 199         {
 200                 M_CheckYE(year, ref era);
 201                 if (month < 1 || month > 12)
 202                         throw new ArgumentOutOfRangeException("month",
 203                                 "Month must be between one and twelve.");
 204                 else if (year == M_MaxYear && month > 10)
 205                         throw new ArgumentOutOfRangeException("month",
 206                                 "Months in year 9378 must be between one and ten.");
 207         }
 208
 209         /// <summary>
 210         /// A protected method checking the calendar day, month, and year
 211         /// and the era number.
 212         /// </summary>
 213         /// <param name="year">An integer representing the calendar year.
 214         /// </param>
 215         /// <param name="month">An integer giving the calendar month.
 216         /// </param>
 217         /// <param name="day">An integer giving the calendar day.
 218         /// </param>
 219         /// <param name="era">The era number.</param>
 220         /// <exception cref="T:System.ArgumentException">
 221         /// The exception is thrown if the era is not equal
 222         /// <see cref="F:PersianEra"/>.
 223         /// </exception>
 224         /// <exception cref="T:System.ArgumentOutOfRangeException">
 225         /// The exception is thrown if the calendar year, month, or day is
 226         /// outside of the allowed range.
 227         /// </exception>
 228         internal void M_CheckYMDE(int year, int month, int day,
 229                                   ref int era)
 230         {
 231                 M_CheckYME(year, month, ref era);
 232                 M_ArgumentInRange("day",
 233                         day, 1, GetDaysInMonth(year, month, era));
 234                 if (year == M_MaxYear && month == 10 && day > 10)
 235                         throw new ArgumentOutOfRangeException("day",
 236                                 "Days in month 10 of year 9378 must" +
 237                                 " be between one and ten.");
 238         }
 239
 240         internal const int epoch = 226895;
 241
 242         // FIXME: this may need a "static". I don't know enough C#.
 243         internal int fixed_from_dmy(int day, int month, int year)
 244         {
 245                 int k = epoch - 1;
 246
 247                 k += 365 * (year - 1);
 248                 k += (8 * year + 21) / 33;
 249                 if (month <= 7)
 250                         k += 31 * (month - 1);
 251                 else
 252                         k += 30 * (month - 1) + 6;
 253                 k += day;
 254
 255                 return k;
 256         }
 257
 258         // FIXME: this may need a "static". I don't know enough C#.
 259         internal int year_from_fixed(int date)
 260         {
 261                 return (33 * (date - epoch) + 3) / 12053 + 1;
 262         }
 263
 264         // FIXME: this may need a "static". I don't know enough C#.
 265         internal void my_from_fixed(out int month, out int year,
 266                 int date)
 267         {
 268                 int day;
 269
 270                 year = year_from_fixed(date);
 271                 day = date - fixed_from_dmy (1, 1, year);
 272                 if (day < 216)
 273                         month = day / 31 + 1;
 274                 else
 275                         month = (day - 6) / 30 + 1;
 276         }
 277
 278         // FIXME: this may need a "static". I don't know enough C#.
 279         internal void dmy_from_fixed(out int day, out int month,
 280                                      out int year, int date)
 281         {
 282                 year = year_from_fixed(date);
 283                 day = date - fixed_from_dmy (1, 1, year);
 284                 if (day < 216) {
 285                         month = day / 31 + 1;
 286                         day = day % 31 + 1;
 287                 } else {
 288                         month = (day-6) / 30 + 1;
 289                         day = (day-6) % 30 + 1;
 290                 }
 291         }
 292
 293         // FIXME: this may need a "static". I don't know enough C#.
 294         internal bool is_leap_year(int year)
 295         {
 296                 return (25 * year + 11) % 33 < 8;
 297         }
 298
 299         /// <summary>
 300         /// Overrideden. Adds months to a given date.
 301         /// </summary>
 302         /// <param name="time">The
 303         /// <see cref="T:System.DateTime"/> to which to add
 304         /// months.
 305         /// </param>
 306         /// <param name="months">The number of months to add.</param>
 307         /// <returns>A new <see cref="T:System.DateTime"/> value, that
 308         /// results from adding <paramref name="months"/> to the specified
 309         /// DateTime.</returns>
 310         /// <exception cref="T:System.ArgumentOutOfRangeException">
 311         /// The exception is thrown if the
 312         /// <see cref="T:System.DateTime"/> return value is not in the years
 313         /// between 1 A.P. and 9999 C.E., inclusive.
 314         /// </exception>
 315         public override DateTime AddMonths(DateTime time, int months)
 316         {
 317                 int rd = CCFixed.FromDateTime(time);
 318                 int day, month, year;
 319
 320                 dmy_from_fixed(out day, out month, out year, rd);
 321                 month += months;
 322                 year += CCMath.div_mod(out month, month, 12);
 323                 rd = fixed_from_dmy(day, month, year);
 324                 DateTime t = CCFixed.ToDateTime(rd);
 325                 t = t.Add(time.TimeOfDay);
 326                 M_CheckDateTime(t);
 327                 return t;
 328         }
 329
 330         /// <summary>
 331         /// Overridden. Adds years to a given date.
 332         /// </summary>
 333         /// <param name="time">The
 334         /// <see cref="T:System.DateTime"/> to which to add
 335         /// years.
 336         /// </param>
 337         /// <param name="years">The number of years to add.</param>
 338         /// <returns>A new <see cref="T:System.DateTime"/> value, that
 339         /// results from adding <paramref name="years"/> to the specified
 340         /// DateTime.</returns>
 341         /// <exception cref="T:System.ArgumentOutOfRangeException">
 342         /// The exception is thrown if the
 343         /// <see cref="T:System.DateTime"/> return value is not in the years
 344         /// between 1 A.P. and 9999 C.E., inclusive.
 345         /// </exception>
 346         public override DateTime AddYears(DateTime time, int years)
 347         {
 348                 int rd = CCFixed.FromDateTime(time);
 349                 int day, month, year;
 350
 351                 dmy_from_fixed(out day, out month, out year, rd);
 352                 year += years;
 353                 rd = fixed_from_dmy(day, month, year);
 354                 DateTime t = CCFixed.ToDateTime(rd);
 355                 t = t.Add(time.TimeOfDay);
 356                 M_CheckDateTime(t);
 357                 return t;
 358         }
 359
 360         /// <summary>
 361         /// Overriden. Gets the day of the month from
 362         /// <paramref name="time"/>.
 363         /// </summary>
 364         /// <param name="time">The
 365         /// <see cref="T:System.DateTime"/> that specifies a
 366         /// date.
 367         /// </param>
 368         /// <returns>An integer giving the day of months, starting with 1.
 369         /// </returns>
 370         /// <exception cref="T:System.ArgumentOutOfRangeException">
 371         /// The exception is thrown if the
 372         /// <see cref="T:System.DateTime"/> parameter is not in the years
 373         /// between 1 A.P. and 9999 C.E., inclusive.
 374         /// </exception>
 375         public override int GetDayOfMonth(DateTime time)
 376         {
 377                 int day, month, year;
 378
 379                 M_CheckDateTime(time);
 380                 int rd = CCFixed.FromDateTime(time);
 381                 dmy_from_fixed(out day, out month, out year, rd);
 382                 return day;
 383         }
 384
 385         /// <summary>
 386         /// Overriden. Gets the day of the week from the specified date.
 387         /// </summary>
 388         /// <param name="time">The
 389         /// <see cref="T:System.DateTime"/> that specifies a
 390         /// date.
 391         /// </param>
 392         /// <returns>An integer giving the day of months, starting with 1.
 393         /// </returns>
 394         /// <exception cref="T:System.ArgumentOutOfRangeException">
 395         /// The exception is thrown if the
 396         /// <see cref="T:System.DateTime"/> parameter is not in the years
 397         /// between 1 A.P. and 9999 C.E., inclusive.
 398         /// </exception>
 399         public override DayOfWeek GetDayOfWeek(DateTime time)
 400         {
 401                 M_CheckDateTime(time);
 402                 int rd = CCFixed.FromDateTime(time);
 403                 return (DayOfWeek)CCFixed.day_of_week(rd);
 404         }
 405
 406         /// <summary>
 407         /// Overridden. Gives the number of the day in the year.
 408         /// </summary>
 409         /// <param name="time">The
 410         /// <see cref="T:System.DateTime"/> that specifies a
 411         /// date.
 412         /// </param>
 413         /// <returns>An integer representing the day of the year,
 414         /// starting with 1.</returns>
 415         /// <exception cref="T:System.ArgumentOutOfRangeException">
 416         /// The exception is thrown if the
 417         /// <see cref="T:System.DateTime"/> parameter is not in the years
 418         /// between 1 A.P. and 9999 C.E., inclusive.
 419         /// </exception>
 420         public override int GetDayOfYear(DateTime time)
 421         {
 422                 M_CheckDateTime(time);
 423                 int rd = CCFixed.FromDateTime(time);
 424                 int year = year_from_fixed(rd);
 425                 int rd1_1 = fixed_from_dmy(1, 1, year);
 426                 return rd - rd1_1 + 1;
 427         }
 428
 429         /// <summary>
 430         /// Overridden. Gives the number of days in the specified month
 431         /// of the given year and era.
 432         /// </summary>
 433         /// <param name="year">An integer that gives the year.
 434         /// </param>
 435         /// <param name="month">An integer that gives the month, starting
 436         /// with 1.</param>
 437         /// <param name="era">An integer that gives the era of the specified
 438         /// year.</param>
 439         /// <returns>An integer that gives the number of days of the
 440         /// specified month.</returns>
 441         /// <exception cref="T:System.ArgumentOutOfRangeException">
 442         /// The exception is thrown, if <paramref name="month"/>,
 443         /// <paramref name="year"/> ,or <paramref name="era"/> is outside
 444         /// the allowed range.
 445         /// </exception>
 446         public override int GetDaysInMonth(int year, int month, int era)
 447         {
 448                 M_CheckYME(year, month, ref era);
 449                 if (month <= 6) {
 450                         return 31;
 451                 } else if (month == 12 && !is_leap_year(year)) {
 452                         return 29;
 453                 } else {
 454                         return 30;
 455                 }
 456         }
 457
 458         /// <summary>
 459         /// Overridden. Gives the number of days of the specified
 460         /// year of the given era.
 461         /// </summary>
 462         /// <param name="year">An integer that specifies the year.
 463         /// </param>
 464         /// <param name="era">An ineger that specifies the era.
 465         /// </param>
 466         /// <returns>An integer that gives the number of days of the
 467         /// specified year.</returns>
 468         /// <exception cref="T:System.ArgumentOutOfRangeExceiption">
 469         /// The exception is thrown, if
 470         /// <paramref name="year"/> or <paramref name="era"/> are outside the
 471         /// allowed range.
 472         /// </exception>
 473         public override int GetDaysInYear(int year, int era)
 474         {
 475                 M_CheckYE(year, ref era);
 476                 return is_leap_year(year) ? 366 : 365;
 477         }
 478
 479
 480         /// <summary>
 481         /// Overridden. Gives the era of the specified date.
 482         /// </summary>
 483         /// <param name="time">The
 484         /// <see cref="T:System.DateTime"/> that specifies a
 485         /// date.
 486         /// </param>
 487         /// <returns>An integer representing the era of the calendar.
 488         /// </returns>
 489         /// <exception cref="T:System.ArgumentOutOfRangeException">
 490         /// The exception is thrown if the
 491         /// <see cref="T:System.DateTime"/> parameter is not in the years
 492         /// between 1 A.P. and 9999 C.E., inclusive.
 493         /// </exception>
 494         public override int GetEra(DateTime time)
 495         {
 496                 M_CheckDateTime(time);
 497                 return PersianEra;
 498         }
 499
 500         public override int GetLeapMonth (int year, int era)
 501         {
 502                 return 0;
 503         }
 504
 505         /// <summary>
 506         /// Overridden. Gives the number of the month of the specified
 507         /// date.
 508         /// </summary>
 509         /// <param name="time">The
 510         /// <see cref="T:System.DateTime"/> that specifies a
 511         /// date.
 512         /// </param>
 513         /// <returns>An integer representing the month,
 514         /// starting with 1.</returns>
 515         /// <exception cref="T:System.ArgumentOutOfRangeException">
 516         /// The exception is thrown if the
 517         /// <see cref="T:System.DateTime"/> parameter is not in the years
 518         /// between 1 A.P. and 9999 C.E., inclusive.
 519         /// </exception>
 520         public override int GetMonth(DateTime time)
 521         {
 522                 M_CheckDateTime(time);
 523                 int rd = CCFixed.FromDateTime(time);
 524                 int month, year;
 525                 my_from_fixed(out month, out year, rd);
 526                 return month;
 527         }
 528
 529         /// <summary>
 530         /// Overridden. Gives the number of months in the specified year
 531         /// and era.
 532         /// </summary>
 533         /// <param name="year">An integer that specifies the year.
 534         /// </param>
 535         /// <param name="era">An integer that specifies the era.
 536         /// </param>
 537         /// <returns>An integer that gives the number of the months in the
 538         /// specified year.</returns>
 539         /// <exception cref="T:System.ArgumentOutOfRangeException">
 540         /// The exception is thrown, if the year or the era are not valid.
 541         /// </exception>
 542         public override int GetMonthsInYear(int year, int era)
 543         {
 544                 M_CheckYE(year, ref era);
 545                 return 12;
 546         }
 547
 548         /// <summary>
 549         /// Overridden. Gives the number of the year of the specified
 550         /// date.
 551         /// </summary>
 552         /// <param name="time">The
 553         /// <see cref="T:System.DateTime"/> that specifies a
 554         /// date.
 555         /// </param>
 556         /// <returns>An integer representing the year,
 557         /// starting with 1.</returns>
 558         /// <exception cref="T:System.ArgumentOutOfRangeException">
 559         /// The exception is thrown if the
 560         /// <see cref="T:System.DateTime"/> parameter is not in the years
 561         /// between 1 A.P. and 9999 C.E., inclusive.
 562         /// </exception>
 563         public override int GetYear(DateTime time)
 564         {
 565                 M_CheckDateTime(time);
 566                 int rd = CCFixed.FromDateTime(time);
 567                 return year_from_fixed(rd);
 568         }
 569
 570         /// <summary>
 571         /// Overridden. Tells whether the given day
 572         /// is a leap day.
 573         /// </summary>
 574         /// <param name="year">An integer that specifies the year in the
 575         /// given era.
 576         /// </param>
 577         /// <param name="month">An integer that specifies the month.
 578         /// </param>
 579         /// <param name="day">An integer that specifies the day.
 580         /// </param>
 581         /// <param name="era">An integer that specifies the era.
 582         /// </param>
 583         /// <returns>A boolean that tells whether the given day is a leap
 584         /// day.
 585         /// </returns>
 586         /// <exception cref="T:System.ArgumentOutOfRangeException">
 587         /// The exception is thrown, if the year, month, day, or era is not
 588         /// valid.
 589         /// </exception>
 590         public override bool IsLeapDay(int year, int month, int day,
 591                                        int era)
 592         {
 593                 M_CheckYMDE(year, month, day, ref era);
 594                 return is_leap_year(year) && month == 12 && day == 30;
 595         }
 596
 597         /// <summary>
 598         /// Overridden. Tells whether the given month
 599         /// is a leap month.
 600         /// </summary>
 601         /// <param name="year">An integer that specifies the year in the
 602         /// given era.
 603         /// </param>
 604         /// <param name="month">An integer that specifies the month.
 605         /// </param>
 606         /// <param name="era">An integer that specifies the era.
 607         /// </param>
 608         /// <returns>A boolean that tells whether the given month is a leap
 609         /// month.
 610         /// </returns>
 611         /// <exception cref="T:System.ArgumentOutOfRangeException">
 612         /// The exception is thrown, if the year, month, or era is not
 613         /// valid.
 614         /// </exception>
 615         public override bool IsLeapMonth(int year, int month, int era)
 616         {
 617                 M_CheckYME(year, month, ref era);
 618                 return false;
 619         }
 620
 621         /// <summary>
 622         /// Overridden. Tells whether the given year
 623         /// is a leap year.
 624         /// </summary>
 625         /// <param name="year">An integer that specifies the year in the
 626         /// given era.
 627         /// </param>
 628         /// <param name="era">An integer that specifies the era.
 629         /// </param>
 630         /// <returns>A boolean that tells whether the given year is a leap
 631         /// year.
 632         /// </returns>
 633         /// <exception cref="T:System.ArgumentOutOfRangeException">
 634         /// The exception is thrown, if the year or era is not
 635         /// valid.
 636         /// </exception>
 637         public override bool IsLeapYear(int year, int era)
 638         {
 639                 M_CheckYE(year, ref era);
 640                 return is_leap_year(year);
 641         }
 642
 643         /// <summary>
 644         /// Overridden. Creates the
 645         /// <see cref="T:System.DateTime"/> from the parameters.
 646         /// </summary>
 647         /// <param name="year">An integer that gives the year in the
 648         /// <paramref name="era"/>.
 649         /// </param>
 650         /// <param name="month">An integer that specifies the month.
 651         /// </param>
 652         /// <param name="day">An integer that specifies the day.
 653         /// </param>
 654         /// <param name="hour">An integer that specifies the hour.
 655         /// </param>
 656         /// <param name="minute">An integer that specifies the minute.
 657         /// </param>
 658         /// <param name="second">An integer that gives the second.
 659         /// </param>
 660         /// <param name="milliseconds">An integer that gives the
 661         /// milliseconds.
 662         /// </param>
 663         /// <param name="era">An integer that specifies the era.
 664         /// </param>
 665         /// <returns>A
 666         /// <see cref="T:system.DateTime"/> representig the date and time.
 667         /// </returns>
 668         /// <exception cref="T:System.ArgumentOutOfRangeException">
 669         /// The exception is thrown, if at least one of the parameters
 670         /// is out of range.
 671         /// </exception>
 672         public override DateTime ToDateTime(int year, int month, int day,
 673                                             int hour, int minute,
 674                                             int second, int millisecond,
 675                                             int era)
 676         {
 677                 M_CheckYMDE(year, month, day, ref era);
 678                 M_CheckHMSM(hour, minute, second, millisecond);
 679                 int rd = fixed_from_dmy(day, month, year);
 680                 return CCFixed.ToDateTime(rd,
 681                         hour, minute, second, millisecond);
 682         }
 683
 684         // FIXME: Calendar.cs and HebrewCalendar.cs are different in
 685         // how they handle this. I have randomly chosen the
 686         // HebrewCalendar.cs implementation.
 687         public override int ToFourDigitYear (int year)
 688         {
 689                 M_ArgumentInRange ("year", year, 0, 99);
 690
 691                 int baseExtra = this.twoDigitYearMax % 100;
 692                 int baseCentury = this.twoDigitYearMax - baseExtra;
 693
 694                 if (year <= baseExtra)
 695                         return baseCentury + year;
 696                 else
 697                         return baseCentury + year - 100;
 698         }
 699
 700         public override CalendarAlgorithmType AlgorithmType {
 701                 get {
 702                         return CalendarAlgorithmType.SolarCalendar;
 703                 }
 704         }
 705
 706         static DateTime PersianMin = new DateTime (622, 3, 21, 0, 0, 0);
 707         static DateTime PersianMax = new DateTime (9999, 12, 31, 11, 59, 59);
 708
 709         public override DateTime MinSupportedDateTime {
 710                 get {
 711                         return PersianMin;
 712                 }
 713         }
 714
 715         public override DateTime MaxSupportedDateTime {
 716                 get {
 717                         return PersianMax;
 718                 }
 719         }
 720 } // class PersianCalendar
 721
 722 } // namespace System.Globalization