// Licensed to the .NET Foundation under one or more agreements. // The .NET Foundation licenses this file to you under the MIT license. // See the LICENSE file in the project root for more information. using System.Diagnostics; namespace System.Globalization { // This abstract class represents a calendar. A calendar reckons time in // divisions such as weeks, months and years. The number, length and start of // the divisions vary in each calendar. // // Any instant in time can be represented as an n-tuple of numeric values using // a particular calendar. For example, the next vernal equinox occurs at (0.0, 0 // , 46, 8, 20, 3, 1999) in the Gregorian calendar. An implementation of // Calendar can map any DateTime value to such an n-tuple and vice versa. The // DateTimeFormat class can map between such n-tuples and a textual // representation such as "8:46 AM March 20th 1999 AD". // // Most calendars identify a year which begins the current era. There may be any // number of previous eras. The Calendar class identifies the eras as enumerated // integers where the current era (CurrentEra) has the value zero. // // For consistency, the first unit in each interval, e.g. the first month, is // assigned the value one. // The calculation of hour/minute/second is moved to Calendar from GregorianCalendar, // since most of the calendars (or all?) have the same way of calcuating hour/minute/second. public abstract class Calendar : ICloneable { // Number of 100ns (10E-7 second) ticks per time unit internal const long TicksPerMillisecond = 10000; internal const long TicksPerSecond = TicksPerMillisecond * 1000; internal const long TicksPerMinute = TicksPerSecond * 60; internal const long TicksPerHour = TicksPerMinute * 60; internal const long TicksPerDay = TicksPerHour * 24; // Number of milliseconds per time unit internal const int MillisPerSecond = 1000; internal const int MillisPerMinute = MillisPerSecond * 60; internal const int MillisPerHour = MillisPerMinute * 60; internal const int MillisPerDay = MillisPerHour * 24; // Number of days in a non-leap year internal const int DaysPerYear = 365; // Number of days in 4 years internal const int DaysPer4Years = DaysPerYear * 4 + 1; // Number of days in 100 years internal const int DaysPer100Years = DaysPer4Years * 25 - 1; // Number of days in 400 years internal const int DaysPer400Years = DaysPer100Years * 4 + 1; // Number of days from 1/1/0001 to 1/1/10000 internal const int DaysTo10000 = DaysPer400Years * 25 - 366; internal const long MaxMillis = (long)DaysTo10000 * MillisPerDay; private int _currentEraValue = -1; private bool _isReadOnly = false; public virtual DateTime MinSupportedDateTime => DateTime.MinValue; public virtual DateTime MaxSupportedDateTime => DateTime.MaxValue; public virtual CalendarAlgorithmType AlgorithmType => CalendarAlgorithmType.Unknown; protected Calendar() { } internal virtual CalendarId ID => CalendarId.UNINITIALIZED_VALUE; // Return the Base calendar ID for calendars that didn't have defined data in calendarData internal virtual CalendarId BaseCalendarID => ID; public bool IsReadOnly => _isReadOnly; public virtual object Clone() { object o = MemberwiseClone(); ((Calendar)o).SetReadOnlyState(false); return o; } public static Calendar ReadOnly(Calendar calendar) { if (calendar == null) { throw new ArgumentNullException(nameof(calendar)); } if (calendar.IsReadOnly) { return calendar; } Calendar clonedCalendar = (Calendar)(calendar.MemberwiseClone()); clonedCalendar.SetReadOnlyState(true); return clonedCalendar; } internal void VerifyWritable() { if (_isReadOnly) { throw new InvalidOperationException(SR.InvalidOperation_ReadOnly); } } internal void SetReadOnlyState(bool readOnly) { _isReadOnly = readOnly; } /// /// This is used to convert CurrentEra(0) to an appropriate era value. /// internal virtual int CurrentEraValue { get { // The following code assumes that the current era value can not be -1. if (_currentEraValue == -1) { Debug.Assert(BaseCalendarID != CalendarId.UNINITIALIZED_VALUE, "[Calendar.CurrentEraValue] Expected a real calendar ID"); _currentEraValue = CalendarData.GetCalendarData(BaseCalendarID).iCurrentEra; } return _currentEraValue; } } public const int CurrentEra = 0; internal int _twoDigitYearMax = -1; internal static void CheckAddResult(long ticks, DateTime minValue, DateTime maxValue) { if (ticks < minValue.Ticks || ticks > maxValue.Ticks) { throw new ArgumentException(SR.Format(SR.Argument_ResultCalendarRange, minValue, maxValue)); } } internal DateTime Add(DateTime time, double value, int scale) { // From ECMA CLI spec, Partition III, section 3.27: // // If overflow occurs converting a floating-point type to an integer, or if the floating-point value // being converted to an integer is a NaN, the value returned is unspecified. // // Based upon this, this method should be performing the comparison against the double // before attempting a cast. Otherwise, the result is undefined. double tempMillis = (value * scale + (value >= 0 ? 0.5 : -0.5)); if (!((tempMillis > -(double)MaxMillis) && (tempMillis < (double)MaxMillis))) { throw new ArgumentOutOfRangeException(nameof(value), value, SR.ArgumentOutOfRange_AddValue); } long millis = (long)tempMillis; long ticks = time.Ticks + millis * TicksPerMillisecond; CheckAddResult(ticks, MinSupportedDateTime, MaxSupportedDateTime); return new DateTime(ticks); } /// /// Returns the DateTime resulting from adding the given number of /// milliseconds to the specified DateTime. The result is computed by rounding /// the number of milliseconds given by value to the nearest integer, /// and adding that interval to the specified DateTime. The value /// argument is permitted to be negative. /// public virtual DateTime AddMilliseconds(DateTime time, double milliseconds) { return Add(time, milliseconds, 1); } /// /// Returns the DateTime resulting from adding a fractional number of /// days to the specified DateTime. The result is computed by rounding the /// fractional number of days given by value to the nearest /// millisecond, and adding that interval to the specified DateTime. The /// value argument is permitted to be negative. /// public virtual DateTime AddDays(DateTime time, int days) { return Add(time, days, MillisPerDay); } /// /// Returns the DateTime resulting from adding a fractional number of /// hours to the specified DateTime. The result is computed by rounding the /// fractional number of hours given by value to the nearest /// millisecond, and adding that interval to the specified DateTime. The /// value argument is permitted to be negative. /// public virtual DateTime AddHours(DateTime time, int hours) { return Add(time, hours, MillisPerHour); } /// /// Returns the DateTime resulting from adding a fractional number of /// minutes to the specified DateTime. The result is computed by rounding the /// fractional number of minutes given by value to the nearest /// millisecond, and adding that interval to the specified DateTime. The /// value argument is permitted to be negative. /// public virtual DateTime AddMinutes(DateTime time, int minutes) { return Add(time, minutes, MillisPerMinute); } /// /// Returns the DateTime resulting from adding the given number of /// months to the specified DateTime. The result is computed by incrementing /// (or decrementing) the year and month parts of the specified DateTime by /// value months, and, if required, adjusting the day part of the /// resulting date downwards to the last day of the resulting month in the /// resulting year. The time-of-day part of the result is the same as the /// time-of-day part of the specified DateTime. /// /// In more precise terms, considering the specified DateTime to be of the /// form y / m / d + t, where y is the /// year, m is the month, d is the day, and t is the /// time-of-day, the result is y1 / m1 / d1 + t, /// where y1 and m1 are computed by adding value months /// to y and m, and d1 is the largest value less than /// or equal to d that denotes a valid day in month m1 of year /// y1. /// public abstract DateTime AddMonths(DateTime time, int months); /// /// Returns the DateTime resulting from adding a number of /// seconds to the specified DateTime. The result is computed by rounding the /// fractional number of seconds given by value to the nearest /// millisecond, and adding that interval to the specified DateTime. The /// value argument is permitted to be negative. /// public virtual DateTime AddSeconds(DateTime time, int seconds) { return Add(time, seconds, MillisPerSecond); } // Returns the DateTime resulting from adding a number of // weeks to the specified DateTime. The // value argument is permitted to be negative. public virtual DateTime AddWeeks(DateTime time, int weeks) { return AddDays(time, weeks * 7); } /// /// Returns the DateTime resulting from adding the given number of /// years to the specified DateTime. The result is computed by incrementing /// (or decrementing) the year part of the specified DateTime by value /// years. If the month and day of the specified DateTime is 2/29, and if the /// resulting year is not a leap year, the month and day of the resulting /// DateTime becomes 2/28. Otherwise, the month, day, and time-of-day /// parts of the result are the same as those of the specified DateTime. /// public abstract DateTime AddYears(DateTime time, int years); /// /// Returns the day-of-month part of the specified DateTime. The returned /// value is an integer between 1 and 31. /// public abstract int GetDayOfMonth(DateTime time); /// /// Returns the day-of-week part of the specified DateTime. The returned value /// is an integer between 0 and 6, where 0 indicates Sunday, 1 indicates /// Monday, 2 indicates Tuesday, 3 indicates Wednesday, 4 indicates /// Thursday, 5 indicates Friday, and 6 indicates Saturday. /// public abstract DayOfWeek GetDayOfWeek(DateTime time); /// /// Returns the day-of-year part of the specified DateTime. The returned value /// is an integer between 1 and 366. /// public abstract int GetDayOfYear(DateTime time); /// /// Returns the number of days in the month given by the year and /// month arguments. /// public virtual int GetDaysInMonth(int year, int month) { return GetDaysInMonth(year, month, CurrentEra); } /// /// Returns the number of days in the month given by the year and /// month arguments for the specified era. /// public abstract int GetDaysInMonth(int year, int month, int era); /// /// Returns the number of days in the year given by the year argument /// for the current era. /// public virtual int GetDaysInYear(int year) { return GetDaysInYear(year, CurrentEra); } /// /// Returns the number of days in the year given by the year argument /// for the current era. /// public abstract int GetDaysInYear(int year, int era); /// /// Returns the era for the specified DateTime value. /// public abstract int GetEra(DateTime time); /// /// Get the list of era values. /// /// The int array of the era names supported in this calendar or null if era is not used. public abstract int[] Eras { get; } // Returns the hour part of the specified DateTime. The returned value is an // integer between 0 and 23. public virtual int GetHour(DateTime time) { return (int)((time.Ticks / TicksPerHour) % 24); } // Returns the millisecond part of the specified DateTime. The returned value // is an integer between 0 and 999. public virtual double GetMilliseconds(DateTime time) { return (double)((time.Ticks / TicksPerMillisecond) % 1000); } // Returns the minute part of the specified DateTime. The returned value is // an integer between 0 and 59. public virtual int GetMinute(DateTime time) { return (int)((time.Ticks / TicksPerMinute) % 60); } // Returns the month part of the specified DateTime. The returned value is an // integer between 1 and 12. public abstract int GetMonth(DateTime time); // Returns the number of months in the specified year in the current era. public virtual int GetMonthsInYear(int year) { return GetMonthsInYear(year, CurrentEra); } // Returns the number of months in the specified year and era. public abstract int GetMonthsInYear(int year, int era); // Returns the second part of the specified DateTime. The returned value is // an integer between 0 and 59. public virtual int GetSecond(DateTime time) { return (int)((time.Ticks / TicksPerSecond) % 60); } /// /// Get the week of year using the FirstDay rule. /// /// /// The CalendarWeekRule.FirstDay rule: Week 1 begins on the first day of the year. /// Assume f is the specifed firstDayOfWeek, /// and n is the day of week for January 1 of the specified year. /// Assign offset = n - f; /// Case 1: offset = 0 /// E.g. /// f=1 /// weekday 0 1 2 3 4 5 6 0 1 /// date 1/1 /// week# 1 2 /// then week of year = (GetDayOfYear(time) - 1) / 7 + 1 /// /// Case 2: offset < 0 /// e.g. /// n=1 f=3 /// weekday 0 1 2 3 4 5 6 0 /// date 1/1 /// week# 1 2 /// This means that the first week actually starts 5 days before 1/1. /// So week of year = (GetDayOfYear(time) + (7 + offset) - 1) / 7 + 1 /// Case 3: offset > 0 /// e.g. /// f=0 n=2 /// weekday 0 1 2 3 4 5 6 0 1 2 /// date 1/1 /// week# 1 2 /// This means that the first week actually starts 2 days before 1/1. /// So Week of year = (GetDayOfYear(time) + offset - 1) / 7 + 1 /// internal int GetFirstDayWeekOfYear(DateTime time, int firstDayOfWeek) { int dayOfYear = GetDayOfYear(time) - 1; // Make the day of year to be 0-based, so that 1/1 is day 0. // Calculate the day of week for the first day of the year. // dayOfWeek - (dayOfYear % 7) is the day of week for the first day of this year. Note that // this value can be less than 0. It's fine since we are making it positive again in calculating offset. int dayForJan1 = (int)GetDayOfWeek(time) - (dayOfYear % 7); int offset = (dayForJan1 - firstDayOfWeek + 14) % 7; Debug.Assert(offset >= 0, "Calendar.GetFirstDayWeekOfYear(): offset >= 0"); return (dayOfYear + offset) / 7 + 1; } private int GetWeekOfYearFullDays(DateTime time, int firstDayOfWeek, int fullDays) { int dayForJan1; int offset; int day; int dayOfYear = GetDayOfYear(time) - 1; // Make the day of year to be 0-based, so that 1/1 is day 0. // Calculate the number of days between the first day of year (1/1) and the first day of the week. // This value will be a positive value from 0 ~ 6. We call this value as "offset". // // If offset is 0, it means that the 1/1 is the start of the first week. // Assume the first day of the week is Monday, it will look like this: // Sun Mon Tue Wed Thu Fri Sat // 12/31 1/1 1/2 1/3 1/4 1/5 1/6 // +--> First week starts here. // // If offset is 1, it means that the first day of the week is 1 day ahead of 1/1. // Assume the first day of the week is Monday, it will look like this: // Sun Mon Tue Wed Thu Fri Sat // 1/1 1/2 1/3 1/4 1/5 1/6 1/7 // +--> First week starts here. // // If offset is 2, it means that the first day of the week is 2 days ahead of 1/1. // Assume the first day of the week is Monday, it will look like this: // Sat Sun Mon Tue Wed Thu Fri Sat // 1/1 1/2 1/3 1/4 1/5 1/6 1/7 1/8 // +--> First week starts here. // Day of week is 0-based. // Get the day of week for 1/1. This can be derived from the day of week of the target day. // Note that we can get a negative value. It's ok since we are going to make it a positive value when calculating the offset. dayForJan1 = (int)GetDayOfWeek(time) - (dayOfYear % 7); // Now, calculate the offset. Subtract the first day of week from the dayForJan1. And make it a positive value. offset = (firstDayOfWeek - dayForJan1 + 14) % 7; if (offset != 0 && offset >= fullDays) { // If the offset is greater than the value of fullDays, it means that // the first week of the year starts on the week where Jan/1 falls on. offset -= 7; } // Calculate the day of year for specified time by taking offset into account. day = dayOfYear - offset; if (day >= 0) { // If the day of year value is greater than zero, get the week of year. return day / 7 + 1; } // Otherwise, the specified time falls on the week of previous year. // Call this method again by passing the last day of previous year. // the last day of the previous year may "underflow" to no longer be a valid date time for // this calendar if we just subtract so we need the subclass to provide us with // that information if (time <= MinSupportedDateTime.AddDays(dayOfYear)) { return GetWeekOfYearOfMinSupportedDateTime(firstDayOfWeek, fullDays); } return GetWeekOfYearFullDays(time.AddDays(-(dayOfYear + 1)), firstDayOfWeek, fullDays); } private int GetWeekOfYearOfMinSupportedDateTime(int firstDayOfWeek, int minimumDaysInFirstWeek) { int dayOfYear = GetDayOfYear(MinSupportedDateTime) - 1; // Make the day of year to be 0-based, so that 1/1 is day 0. int dayOfWeekOfFirstOfYear = (int)GetDayOfWeek(MinSupportedDateTime) - dayOfYear % 7; // Calculate the offset (how many days from the start of the year to the start of the week) int offset = (firstDayOfWeek + 7 - dayOfWeekOfFirstOfYear) % 7; if (offset == 0 || offset >= minimumDaysInFirstWeek) { // First of year falls in the first week of the year return 1; } int daysInYearBeforeMinSupportedYear = DaysInYearBeforeMinSupportedYear - 1; // Make the day of year to be 0-based, so that 1/1 is day 0. int dayOfWeekOfFirstOfPreviousYear = dayOfWeekOfFirstOfYear - 1 - (daysInYearBeforeMinSupportedYear % 7); // starting from first day of the year, how many days do you have to go forward // before getting to the first day of the week? int daysInInitialPartialWeek = (firstDayOfWeek - dayOfWeekOfFirstOfPreviousYear + 14) % 7; int day = daysInYearBeforeMinSupportedYear - daysInInitialPartialWeek; if (daysInInitialPartialWeek >= minimumDaysInFirstWeek) { // If the offset is greater than the minimum Days in the first week, it means that // First of year is part of the first week of the year even though it is only a partial week // add another week day += 7; } return day / 7 + 1; } protected virtual int DaysInYearBeforeMinSupportedYear => 365; /// /// Returns the week of year for the specified DateTime. The returned value is an /// integer between 1 and 53. /// public virtual int GetWeekOfYear(DateTime time, CalendarWeekRule rule, DayOfWeek firstDayOfWeek) { if (firstDayOfWeek < DayOfWeek.Sunday || firstDayOfWeek > DayOfWeek.Saturday) { throw new ArgumentOutOfRangeException( nameof(firstDayOfWeek), firstDayOfWeek, SR.Format(SR.ArgumentOutOfRange_Range, DayOfWeek.Sunday, DayOfWeek.Saturday)); } return rule switch { CalendarWeekRule.FirstDay => GetFirstDayWeekOfYear(time, (int)firstDayOfWeek), CalendarWeekRule.FirstFullWeek => GetWeekOfYearFullDays(time, (int)firstDayOfWeek, 7), CalendarWeekRule.FirstFourDayWeek => GetWeekOfYearFullDays(time, (int)firstDayOfWeek, 4), _ => throw new ArgumentOutOfRangeException( nameof(rule), rule, SR.Format(SR.ArgumentOutOfRange_Range, CalendarWeekRule.FirstDay, CalendarWeekRule.FirstFourDayWeek)), }; } /// /// Returns the year part of the specified DateTime. The returned value is an /// integer between 1 and 9999. /// public abstract int GetYear(DateTime time); /// /// Checks whether a given day in the current era is a leap day. /// This method returns true if the date is a leap day, or false if not. /// public virtual bool IsLeapDay(int year, int month, int day) { return IsLeapDay(year, month, day, CurrentEra); } /// /// Checks whether a given day in the specified era is a leap day. /// This method returns true if the date is a leap day, or false if not. /// public abstract bool IsLeapDay(int year, int month, int day, int era); /// /// Checks whether a given month in the current era is a leap month. /// This method returns true if month is a leap month, or false if not. /// public virtual bool IsLeapMonth(int year, int month) { return IsLeapMonth(year, month, CurrentEra); } /// /// Checks whether a given month in the specified era is a leap month. This method returns true if /// month is a leap month, or false if not. /// public abstract bool IsLeapMonth(int year, int month, int era); /// /// Returns the leap month in a calendar year of the current era. /// This method returns 0 if this calendar does not have leap month, /// or this year is not a leap year. /// public virtual int GetLeapMonth(int year) { return GetLeapMonth(year, CurrentEra); } /// /// Returns the leap month in a calendar year of the specified era. /// This method returns 0 if this calendar does not have leap month, /// or this year is not a leap year. /// public virtual int GetLeapMonth(int year, int era) { if (!IsLeapYear(year, era)) { return 0; } int monthsCount = GetMonthsInYear(year, era); for (int month = 1; month <= monthsCount; month++) { if (IsLeapMonth(year, month, era)) { return month; } } return 0; } /// /// Checks whether a given year in the current era is a leap year. /// This method returns true if year is a leap year, or false if not. /// public virtual bool IsLeapYear(int year) { return IsLeapYear(year, CurrentEra); } /// /// Checks whether a given year in the specified era is a leap year. /// This method returns true if year is a leap year, or false if not. /// public abstract bool IsLeapYear(int year, int era); /// /// Returns the date and time converted to a DateTime value. /// Throws an exception if the n-tuple is invalid. /// public virtual DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond) { return ToDateTime(year, month, day, hour, minute, second, millisecond, CurrentEra); } /// /// Returns the date and time converted to a DateTime value. /// Throws an exception if the n-tuple is invalid. /// public abstract DateTime ToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era); internal virtual bool TryToDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int era, out DateTime result) { result = DateTime.MinValue; try { result = ToDateTime(year, month, day, hour, minute, second, millisecond, era); return true; } catch (ArgumentException) { return false; } } internal virtual bool IsValidYear(int year, int era) { return year >= GetYear(MinSupportedDateTime) && year <= GetYear(MaxSupportedDateTime); } internal virtual bool IsValidMonth(int year, int month, int era) { return IsValidYear(year, era) && month >= 1 && month <= GetMonthsInYear(year, era); } internal virtual bool IsValidDay(int year, int month, int day, int era) { return IsValidMonth(year, month, era) && day >= 1 && day <= GetDaysInMonth(year, month, era); } /// /// Returns and assigns the maximum value to represent a two digit year. /// This value is the upper boundary of a 100 year range that allows a /// two digit year to be properly translated to a four digit year. /// For example, if 2029 is the upper boundary, then a two digit value of /// 30 should be interpreted as 1930 while a two digit value of 29 should /// be interpreted as 2029. In this example, the 100 year range would be /// from 1930-2029. See ToFourDigitYear(). /// public virtual int TwoDigitYearMax { get => _twoDigitYearMax; set { VerifyWritable(); _twoDigitYearMax = value; } } /// /// Converts the year value to the appropriate century by using the /// TwoDigitYearMax property. For example, if the TwoDigitYearMax value is 2029, /// then a two digit value of 30 will get converted to 1930 while a two digit /// value of 29 will get converted to 2029. /// public virtual int ToFourDigitYear(int year) { if (year < 0) { throw new ArgumentOutOfRangeException(nameof(year), year, SR.ArgumentOutOfRange_NeedNonNegNum); } if (year < 100) { return (TwoDigitYearMax / 100 - (year > TwoDigitYearMax % 100 ? 1 : 0)) * 100 + year; } // If the year value is above 100, just return the year value. Don't have to do // the TwoDigitYearMax comparison. return year; } /// /// Return the tick count corresponding to the given hour, minute, second. /// Will check the if the parameters are valid. /// internal static long TimeToTicks(int hour, int minute, int second, int millisecond) { if (hour < 0 || hour >= 24 || minute < 0 || minute >= 60 || second < 0 || second >= 60) { throw new ArgumentOutOfRangeException(null, SR.ArgumentOutOfRange_BadHourMinuteSecond); } if (millisecond < 0 || millisecond >= MillisPerSecond) { throw new ArgumentOutOfRangeException( nameof(millisecond), millisecond, SR.Format(SR.ArgumentOutOfRange_Range, 0, MillisPerSecond - 1)); } return InternalGlobalizationHelper.TimeToTicks(hour, minute, second) + millisecond * TicksPerMillisecond; } internal static int GetSystemTwoDigitYearSetting(CalendarId CalID, int defaultYearValue) { int twoDigitYearMax = CalendarData.GetTwoDigitYearMax(CalID); return twoDigitYearMax >= 0 ? twoDigitYearMax : defaultYearValue; } } }