/corlib/System.Globalization/CalendricalCalculations.cs

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// CalendricalCalculations.cs

//

// (C) Ulrich Kunitz 2002

//



//

// Copyright (C) 2004 Novell, Inc (http://www.novell.com)

//

// Permission is hereby granted, free of charge, to any person obtaining

// a copy of this software and associated documentation files (the

// "Software"), to deal in the Software without restriction, including

// without limitation the rights to use, copy, modify, merge, publish,

// distribute, sublicense, and/or sell copies of the Software, and to

// permit persons to whom the Software is furnished to do so, subject to

// the following conditions:

// 

// The above copyright notice and this permission notice shall be

// included in all copies or substantial portions of the Software.

// 

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE

// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION

// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION

// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

//



namespace System.Globalization {



//using System.Collections;

/*

/// <summary>A class that provides mathematical functions.</summary>

/// <remarks>

/// <para>

/// We are breaking the .Net

/// naming conventions to be compatible to the "Calendrical Calculations"

/// bool. 

/// </para>

/// </remarks>

internal class CCMath {

	/// <summary>

	/// A static method which rounds a double value.

	/// </summary>

	/// <param name="x">The double value to round.</param>

	/// <returns>The rounded double.</returns>

	public static double round(double x) {

		return System.Math.Floor(x+0.5);

	}



	/// <summary>

	/// A static method that computes the remainder of the division

	/// of two doubles.

	/// </summary>

	/// <param name="x">The double value which is divided.</param>

	/// <param name="y">The divisor.</param>

	/// <returns>The remainder as double value.</returns>

	public static double mod(double x, double y) {

		return x - y * System.Math.Floor(x/y);

	}



	/// <summary>

	/// The static method divides two integers.

	/// </summary>

	/// <param name="x">The integer x value.</param>

	/// <param name="y">The integer y value.</param>

	/// <returns>The qotient of x and y defined by floor(x/y).

	/// </returns>

	/// <remarks>

	/// Please notify that the function is not compatible to the standard

	/// integer divide operation /.

	/// </remarks>

	public static int div(int x, int y) {

		return (int)System.Math.Floor((double)x/(double)y);

	}



	/// <summary>

	/// The static method computes the remainder of two integers.

	/// </summary>

	/// <param name="x">The integer value which will be divided.</param>

	/// <param name="y">The divisor integer value.</param>

	/// <returns> The remainder as integer value.</returns>

	/// <remarks>

	/// Please notify that the method is not compatible to the C#

	/// remainder operation %.

	/// </remarks>

	public static int mod(int x, int y) {

		return x - y * div(x, y);

	}



	/// <summary>

	/// A static method that combines integer division and remainder

	/// computation.

	/// </summary>

	/// <param name="remainder">Remainder integer output value.

	/// </param>

	/// <param name="x">Integer to be divided.</param>

	/// <param name="y">Divisor integer value.</param>

	/// <returns>The quotient as integer.</returns>

	/// <seealso cref="M:div"/>

	/// <seealso cref="M:mod"/>

	public static int div_mod(out int remainder, int x, int y) {

		int d = div(x, y);

		remainder = x - y * d;

		return d;

	}



	/// <summary>

	/// A static method returning the sign of the argument.

	/// </summary>

	/// <param name="x">The double argument.</param>

	/// <returns>An integer value: -1 for a negative argument;

	/// 0 for a zero argument, and 1 for a positive argument.

	/// </returns>

	public static int signum(double x) {

		if (x < 0.0)

			return -1;

		if (x == 0.0)

			return 0;

		return 1;

	}



	/// <summary>

	/// A static method returning the sign of the integer

	/// argument.

	/// </summary>

	/// <param name="x">The integer argument.</param>

	/// <returns>An integer value: -1 for a negative argument;

	/// 0 for a zero argument, and 1 for a positive argument.

	/// </returns>

	public static int signum(int x) {

		if (x < 0)

			return -1;

		if (x == 0)

			return 0;

		return 1;

	}



	/// <summary>

	/// An adjusted remainder function as defined in "Calendrical

	/// Calculations".

	/// </summary>

	/// <param name="x">The double x argument.</param>

	/// <param name="y">The double y argument, the divisor.</param>

	/// <returns>A double value representing remainder; but instead 0.0

	/// the divisor y is returned.

	/// </returns>

	public static double amod(double x, double y) {

		double d = mod(x, y);

		return (d == 0.0) ? y : d;

	}



	/// <summary>

	/// The adjusted remainder functions for integers as defined in

	/// "Calendrical Calculations".

	/// </summary>

	/// <param name="x">The integer argument to be divided.</param>

	/// <param name="y">The integer divisor argument.</param>

	/// <returns>The remainder as an integer; however instead 0 

	/// is the divisor y returned.

	/// </returns>

	public static int amod(int x, int y) {

		int i = mod(x, y);

		return (i == 0) ? y : i;

	}

}

*/



/// <summary>The class implements methods to handle the fixed date value from

/// the "Calendrical Calculations" books.

/// </summary>

/// <remarks>

/// <para>

/// For implementing the Calendar classes I used the algorithms from the

/// book "Calendrical Calculations" by Nachum Dershowitz and Edward M.

/// Rheingold, second reprint 1998. Trying to prevent the introduction of new

/// bugs, I implemented their algorithms in the

/// <see cref="N:CalendricalCalculations"/>

/// namespace and wrapped it in the calendar classes.

/// </para>

/// <para>

/// The fixed day number is also known as R.D. - rata die.

/// Midnight at the onset of Monday,

/// January 1, year 1 (Gregorian) is R.D. 1.

/// </para>

/// <para>Here are all my references:</para>

/// <list type="table">

/// <item><description>

/// [1] Nachum Dershowitz and Edward M. Rheingold: "Calendrical Calculations";

/// Cambridge University Press; second reprint 1998.

/// </description></item>

/// <item><description>

/// [2] P. Kenneth Seidelmann (ed.): "Explanatory Supplement to the Astronomical

/// Almanac"; University Science Books, Sausalito; 1992 

/// </description></item>

/// <item><description>

/// [3] F. Richard Stephenson: "Historical Eclipses and Earth Rotation";

/// Cambridge University Press; 1997

/// </description></item>

/// </list>

/// </remarks>

internal class CCFixed {

	/// <summary>The method computes the

	/// <see cref="T:System.DateTime"/>

	/// from a fixed day number.

	/// </summary>

	/// <param name="date">A integer representing the fixed day number.

	/// </param>

	/// <returns>The <see cref="T:System.DateTime"/> representing

	/// the date.

	/// </returns>

	public static System.DateTime ToDateTime(int date) {

		long ticks = (date - 1) * System.TimeSpan.TicksPerDay;

		return new System.DateTime(ticks);

	}



	/// <summary>The method computes the

	/// <see cref="T:System.DateTime"/>

	/// from a fixed day number and time arguments.

	/// </summary>

	/// <param name="date">An integer representing the fixed day number.

	/// </param>

	/// <param name="hour">An integer argument specifying the hour.

	/// </param>

	/// <param name="minute">An integer argument specifying the minute.

	/// </param>

	/// <param name="second">An integer argument giving the second.

	/// </param>

	/// <param name="milliseconds">An double argument specifying

	/// the milliseconds. Notice that

	/// <see cref="T:System.DateTime"/> has 100 nanosecond resolution.

	/// </param>

	/// <returns>The <see cref="T:System.DateTime"/> representing

	/// the date.

	/// </returns>

	public static System.DateTime ToDateTime(int date,

		int hour, int minute, int second, double milliseconds)

	{

		System.DateTime time = ToDateTime(date);

		time = time.AddHours(hour);

		time = time.AddMinutes(minute);

		time = time.AddSeconds(second);

		return time.AddMilliseconds(milliseconds);

	}



	/// <summary>

	/// A static method computing the fixed day number from a 

	/// <see cref="T:System.DateTime"/> value.

	/// </summary>

	/// <param name="time">A

	/// <see cref="T:System.DateTime"/> value representing the date.

	/// </param>

	/// <returns>The fixed day number as integer representing the date.

	/// </returns>

	public static int FromDateTime(System.DateTime time) {

		return 1 + (int)(time.Ticks / System.TimeSpan.TicksPerDay);

	}



	/// <summary>

	/// The static method computes the <see cref="T:DayOfWeek"/>.

	/// </summary>

	/// <param name="date">An integer representing the fixed day number.

	/// </param>

	/// <returns>The day of week.</returns>

	public static DayOfWeek day_of_week(int date) {

		return (DayOfWeek)(date % 7);//CCMath.mod(date, 7);

	}



	/// <summary>

	/// The static method computes the date of a day of week on or before

	/// a particular date.

	/// </summary>

	/// <param name="date">An integer representing the date as

	/// fixed day number.

	/// </param>

	/// <param name="k">An integer representing the day of the week,

	/// starting with 0 for sunday.

	/// </param>

	/// <returns>The fixed day number of the day of week specified by k

	/// on or before the given date.

	/// </returns>

	public static int kday_on_or_before(int date, int k) {

		return date - (int)day_of_week(date-k);

	}



	/// <summary>

	/// The static method computes the date of a day of week on or after

	/// a particular date.

	/// </summary>

	/// <param name="date">An integer representing the date as

	/// fixed day number.

	/// </param>

	/// <param name="k">An integer representing the day of the week,

	/// starting with 0 for sunday.

	/// </param>

	/// <returns>The fixed day number of the day of week specified by k

	/// on or after the given date.

	/// </returns>

	public static int kday_on_or_after(int date, int k) {

		return kday_on_or_before(date+6, k);

	}



	/// <summary>

	/// The static method computes the date of a day of week that is

	/// nearest to a particular date.

	/// </summary>

	/// <param name="date">An integer representing the date as

	/// fixed day number.

	/// </param>

	/// <param name="k">An integer representing the day of the week,

	/// starting with 0 for sunday.

	/// </param>

	/// <returns>The fixed day number of the day of week neares to the

	/// given date.

	/// </returns>

	public static int kd_nearest(int date, int k) {

		return kday_on_or_before(date+3, k);

	}



	/// <summary>

	/// The static method computes the date of a day of week after

	/// a particular date.

	/// </summary>

	/// <param name="date">An integer representing the date as

	/// fixed day number.

	/// </param>

	/// <param name="k">An integer representing the day of the week,

	/// starting with 0 for sunday.

	/// </param>

	/// <returns>The fixed day number of the day of week specified by k

	/// after the given date.

	/// </returns>

	public static int kday_after(int date, int k) {

		return kday_on_or_before(date+7, k);

	}



	/// <summary>

	/// The static method computes the date of a day of week before

	/// a particular date.

	/// </summary>

	/// <param name="date">An integer representing the date as

	/// fixed day number.

	/// </param>

	/// <param name="k">An integer representing the day of the week,

	/// starting with 0 for sunday.

	/// </param>

	/// <returns>The fixed day number of the day of week specified by k

	/// before the given date.

	/// </returns>

	public static int kday_before(int date, int k) {

		return kday_on_or_before(date-1, k);

	}

} // class CCFixed





/// <summary>

/// A class encapsulating the functions of the Gregorian calendar as static

/// methods.

/// </summary>

/// <remarks>

/// <para>

/// This class is not compatible to

/// <see cref="T:System.Globalization.GregorianCalendar"/>.

/// </para>

/// <para>

/// The fixed day number is also known as R.D. - rata die.

/// Midnight at the onset of Monday,

/// January 1, year 1 (Gregorian) is R.D. 1.

/// </para>

/// <seealso cref="T:CCFixed"/>

/// </remarks>

internal class CCGregorianCalendar {

	/// <summary>An integer defining the epoch of the Gregorian calendar

	/// as fixed day number.</summary>

	/// <remarks>The epoch is January 3, 1 C.E. (Julian).</remarks>

	const int epoch = 1;



	/// <summary>The enumeration defines the months of the Gregorian

	/// calendar.

	/// </summary>

	public enum Month {

		/// <summary>

		/// January.

		/// </summary>

		january = 1,

		/// <summary>

		/// February.

		/// </summary>

		february,

		/// <summary>

		/// March.

		/// </summary>

		march,

		/// <summary>

		/// April.

		/// </summary>

		april,

		/// <summary>

		/// May.

		/// </summary>

		may,

		/// <summary>

		/// June.

		/// </summary>

		june,

		/// <summary>

		/// July.

		/// </summary>

		july,

		/// <summary>

		/// August.

		/// </summary>

		august,

		/// <summary>

		/// September.

		/// </summary>

		september,

		/// <summary>

		/// October.

		/// </summary>

		october,

		/// <summary>

		/// November.

		/// </summary>

		november,

		/// <summary>

		/// December.

		/// </summary>

		december

	};





	/// <summary>

	/// The method tells whether the year is a leap year.

	/// </summary>

	/// <param name="year">An integer representing the Gregorian year.

	/// </param>

	/// <returns>A boolean which is true if <paramref name="year"/> is

	/// a leap year.

	/// </returns>

	public static bool is_leap_year(int year) {

		if (year % 4 != 0)

			return false;

		switch (year % 400) {

		case 100:

			return false;

		case 200:

			return false;

		case 300:

			return false;

		}

		return true;

	}



	/// <summary>

	/// The method returns the fixed day number of the given Gregorian

	/// date.

	/// </summary>

	/// <param name="day">An integer representing the day of the month,

	/// counting from 1.

	/// </param>

	/// <param name="month">An integer representing the month in the

	/// Gregorian year.

	/// </param>

	/// <param name="year">An integer representing the Gregorian year.

	/// Non-positive values are allowed also.

	/// </param>

	/// <returns>An integer value representing the fixed day number.

	/// </returns>

	public static int fixed_from_dmy(int day, int month, int year) {

		int k = epoch - 1;

		k += 365 * (year-1);

		//k += CCMath.div(year-1, 4);

		//k -= CCMath.div(year-1, 100);

		//k += CCMath.div(year-1, 400);

		//k += CCMath.div(367*month-362, 12);

		k += (year - 1) / 4;

		k -= (year - 1) / 100;

		k += (year - 1) / 400;

		k += (367 * month - 362) / 12;

		if (month > 2) {

			k -= is_leap_year(year) ? 1 : 2;

		}



		k += day;



		return k;

	}



	/// <summary>

	/// The method computes the Gregorian year from a fixed day number.

	/// </summary>

	/// <param name="date">The fixed day number.

	/// </param>

	/// <returns>An integer value giving the Gregorian year of the date.

	/// </returns>

	public static int year_from_fixed(int date) {

		int d		= date - epoch;

		int n_400 = d / 146097;

		d %= 146097;

		int n_100 = d / 36524;

		d %= 36524;

		int n_4 = d / 1461;

		d %= 1461;

		int n_1 = d / 365;

		//int n_400	= CCMath.div_mod(out d, d, 146097);

		//int n_100	= CCMath.div_mod(out d, d, 36524);

		//int n_4		= CCMath.div_mod(out d, d, 1461);

		//int n_1		= CCMath.div(d, 365);



		int year = 400*n_400 + 100*n_100 + 4*n_4 + n_1;

		return (n_100 == 4 || n_1 == 4) ? year : year + 1;

	}



	/// <summary>

	/// The method computes the Gregorian year and month from a fixed day

	/// number.

	/// </summary>

	/// <param name="month">The output value giving the Gregorian month.

	/// </param>

	/// <param name="year">The output value giving the Gregorian year.

	/// </param>

	/// <param name="date">An integer value specifying the fixed day

	/// number.</param>

	public static void my_from_fixed(out int month, out int year,

		int date)

	{

		year = year_from_fixed(date);



		int prior_days = date - fixed_from_dmy(1, (int)Month.january,

			year);

		

		int correction;

		if (date < fixed_from_dmy(1, (int)Month.march, year)) {

			correction = 0;

		} else if (is_leap_year(year)) {

			correction = 1;

		} else {

			correction = 2;

		}



		//month = CCMath.div(12 * (prior_days + correction) + 373, 367);

		month = (12 * (prior_days + correction) + 373) / 367;



	}



	/// <summary>

	/// The method computes the Gregorian year, month, and day from a

	/// fixed day number.

	/// </summary>

	/// <param name="day">The output value returning the day of the

	/// month.

	/// </param>

	/// <param name="month">The output value giving the Gregorian month.

	/// </param>

	/// <param name="year">The output value giving the Gregorian year.

	/// </param>

	/// <param name="date">An integer value specifying the fixed day

	/// number.</param>

	public static void dmy_from_fixed(out int day, out int month,

		out int year,

		int date)

	{

		my_from_fixed(out month, out year, date);

		day = date - fixed_from_dmy(1, month, year) + 1;

	}



	/// <summary>A method computing the Gregorian month from a fixed

	/// day number.

	/// </summary>

	/// <param name="date">An integer specifying the fixed day number.

	/// </param>

	/// <returns>An integer value representing the Gregorian month.

	/// </returns>

	public static int month_from_fixed(int date) {

		int month, year;



		my_from_fixed(out month, out year, date);

		return month;

	}



	/// <summary>

	/// A method computing the day of the month from a fixed day number.

	/// </summary>

	/// <param name="date">An integer specifying the fixed day number.

	/// </param>

	/// <returns>An integer value representing the day of the month.

	/// </returns>

	public static int day_from_fixed(int date) {

		int day, month, year;



		dmy_from_fixed(out day, out month, out year, date);

		return day;

	}



	/// <summary>

	/// The method computes the difference between two Gregorian dates.

	/// </summary>

	/// <param name="dayA">The integer parameter gives the day of month

	/// of the first date.

	/// </param>

	/// <param name="monthA">The integer parameter gives the Gregorian

	/// month of the first date.

	/// </param>

	/// <param name="yearA">The integer parameter gives the Gregorian

	/// year of the first date.

	/// </param>

	/// <param name="dayB">The integer parameter gives the day of month

	/// of the second date.

	/// </param>

	/// <param name="monthB">The integer parameter gives the Gregorian

	/// month of the second date.

	/// </param>

	/// <param name="yearB">The integer parameter gives the Gregorian

	/// year of the second date.

	/// </param>

	/// <returns>An integer giving the difference of days from the first

	/// the second date.

	/// </returns>

	public static int date_difference(int dayA, int monthA, int yearA,

		int dayB, int monthB, int yearB)

	{

		return	fixed_from_dmy(dayB, monthB, yearB) -

			fixed_from_dmy(dayA, monthA, yearA);

	}



	/// <summary>

	/// The method computes the number of the day in the year from

	/// a Gregorian date.

	/// </summary>

	/// <param name="day">An integer representing the day of the month,

	/// counting from 1.

	/// </param>

	/// <param name="month">An integer representing the month in the

	/// Gregorian year.

	/// </param>

	/// <param name="year">An integer representing the Gregorian year.

	/// Non-positive values are allowed also.

	/// </param>

	/// <returns>An integer value giving the number of the day in the

	/// Gregorian year, counting from 1.

	/// </returns>

	public static int day_number(int day, int month, int year) {

		return date_difference(31, (int)Month.december, year-1,

			day, month, year);

	}



	/// <summary>

	/// The method computes the days remaining in the given Gregorian

	/// year from a Gregorian date.

	/// </summary>

	/// <param name="day">An integer representing the day of the month,

	/// counting from 1.

	/// </param>

	/// <param name="month">An integer representing the month in the

	/// Gregorian year.

	/// </param>

	/// <param name="year">An integer representing the Gregorian year.

	/// Non-positive values are allowed also.

	/// </param>

	/// <returns>An integer value giving the number of days remaining in

	/// the Gregorian year.

	/// </returns>

	public static int days_remaining(int day, int month, int year) {

		return date_difference(day, month, year,

			31, (int)Month.december, year);

	}



	// Helper functions for the Gregorian calendars.



	/// <summary>

	/// Adds months to the given date.

	/// </summary>

	/// <param name="time">The

	/// <see cref="T:System.DateTime"/> to which to add

	/// months.

	/// </param>

	/// <param name="months">The number of months to add.</param>

	/// <returns>A new <see cref="T:System.DateTime"/> value, that

	/// results from adding <paramref name="months"/> to the specified

	/// DateTime.</returns>

	public static System.DateTime AddMonths(System.DateTime time,

		int months)

	{

		int rd = CCFixed.FromDateTime(time);

		int day, month, year;

		dmy_from_fixed(out day, out month, out year, rd);

		month += months;

		int maxday = GetDaysInMonth (year, month);

		if (day > maxday)

			day = maxday;

		rd = fixed_from_dmy(day, month, year);

		System.DateTime t = CCFixed.ToDateTime(rd);

		return t.Add(time.TimeOfDay);

	}



	/// <summary>

	/// Adds years to the given date.

	/// </summary>

	/// <param name="time">The

	/// <see cref="T:System.DateTime"/> to which to add

	/// months.

	/// </param>

	/// <param name="years">The number of years to add.</param>

	/// <returns>A new <see cref="T:System.DateTime"/> value, that

	/// results from adding <paramref name="years"/> to the specified

	/// DateTime.</returns>

	public static System.DateTime AddYears(System.DateTime time,

		int years)

	{

		int rd = CCFixed.FromDateTime(time);

		int day, month, year;

		dmy_from_fixed(out day, out month, out year, rd);

		year += years;

		int maxday = GetDaysInMonth (year, month);

		if (day > maxday)

			day = maxday;

		rd = fixed_from_dmy(day, month, year);

		System.DateTime t = CCFixed.ToDateTime(rd);

		return t.Add(time.TimeOfDay);

	}



	/// <summary>

	/// Gets the of the month from <paramref name="time"/>.

	/// </summary>

	/// <param name="time">The

	/// <see cref="T:System.DateTime"/> that specifies a

	/// date.

	/// </param>

	/// <returns>An integer giving the day of months, starting with 1.

	/// </returns>

	public static int GetDayOfMonth(System.DateTime time) {

		return day_from_fixed(CCFixed.FromDateTime(time));

	}



	/// <summary>

	/// The method gives the number of the day in the year.

	/// </summary>

	/// <param name="time">The

	/// <see cref="T:System.DateTime"/> that specifies a

	/// date.

	/// </param>

	/// <returns>An integer representing the day of the year,

	/// starting with 1.</returns>

	public static int GetDayOfYear(System.DateTime time) {

		int rd = CCFixed.FromDateTime(time);

		int year = year_from_fixed(rd);

		int rd1_1 = fixed_from_dmy(1, 1, year);

		return rd - rd1_1 + 1;

	}



	/// <summary>

	/// A method that gives the number of days of the specified

	/// month of the <paramref name="year"/>.

	/// </summary>

	/// <param name="year">An integer that gives the year in the current

	/// era.</param>

	/// <param name="month">An integer that gives the month, starting

	/// with 1.</param>

	/// <returns>An integer that gives the number of days of the

	/// specified month.</returns>

	public static int GetDaysInMonth(int year, int month) {

		int rd1 = fixed_from_dmy(1, month, year);

		int rd2 = fixed_from_dmy(1, month+1, year);

		return rd2 - rd1;

	}



	/// <summary>

	/// The method gives the number of days in the specified year.

	/// </summary>

	/// <param name="year">An integer that gives the year.

	/// </param>

	/// <returns>An integer that gives the number of days of the

	/// specified year.</returns>

	public static int GetDaysInYear(int year) {

		int rd1 = fixed_from_dmy(1, 1, year);

		int rd2 = fixed_from_dmy(1, 1, year+1);

		return rd2 - rd1;

	}



	/// <summary>

	/// The method gives the number of the month of the specified

	/// date.

	/// </summary>

	/// <param name="time">The

	/// <see cref="T:System.DateTime"/> that specifies a

	/// date.

	/// </param>

	/// <returns>An integer representing the month, 

	/// starting with 1.</returns>

	public static int GetMonth(System.DateTime time) {

		return month_from_fixed(CCFixed.FromDateTime(time));

	}



	/// <summary>

	/// The method gives the number of the year of the specified

	/// date.

	/// </summary>

	/// <param name="time">The

	/// <see cref="T:System.DateTime"/> that specifies a

	/// date.

	/// </param>

	/// <returns>An integer representing the year. 

	/// </returns>

	public static int GetYear(System.DateTime time) {

		return year_from_fixed(CCFixed.FromDateTime(time));

	}



	/// <summary>

	/// A virtual method that tells whether the given day

	/// is a leap day.

	/// </summary>

	/// <param name="year">An integer that specifies the year.

	/// </param>

	/// <param name="month">An integer that specifies the month.

	/// </param>

	/// <param name="day">An integer that specifies the day.

	/// </param>

	/// <returns>A boolean that tells whether the given day is a leap

	/// day.

	/// </returns>

	public static bool IsLeapDay(int year, int month, int day) {

		return is_leap_year(year) && month == 2 && day == 29;

	}



	/// <summary>

	/// A method that creates the

	/// <see cref="T:System.DateTime"/> from the parameters.

	/// </summary>

	/// <param name="year">An integer that gives the year

	/// </param>

	/// <param name="month">An integer that specifies the month.

	/// </param>

	/// <param name="day">An integer that specifies the day.

	/// </param>

	/// <param name="hour">An integer that specifies the hour.

	/// </param>

	/// <param name="minute">An integer that specifies the minute.

	/// </param>

	/// <param name="second">An integer that gives the second.

	/// </param>

	/// <param name="milliseconds">An integer that gives the

	/// milliseconds.

	/// </param>

	/// <returns>A

	/// <see cref="T:system.DateTime"/> representig the date and time.

	/// </returns>

	public static System.DateTime ToDateTime(int year, int month, int day,

		int hour, int minute, int second, int milliseconds)

	{

		return CCFixed.ToDateTime(fixed_from_dmy(day, month, year),

			hour, minute, second, milliseconds);

	}

} // class CCGregorianCalendar



/*

/// <summary>

/// A class encapsulating the functions of the Julian calendar as static

/// methods.

/// </summary>

/// <remarks>

/// <para>The algorithms don't support a year 0. Years before Common Era

/// (B.C.E. or B.C.) are negative and years of Common Era (C.E. or A.D.)

/// are positive.

/// </para>

/// <para>

/// This class is not compatible to

/// <see cref="T:System.Globalization.JulianCalendar"/>.

/// </para>

/// <seealso cref="T:CCFixed"/>

/// </remarks>

internal class CCJulianCalendar {

	/// <summary>An integer defining the epoch of the Julian calendar

	/// as fixed day number.</summary>

	/// <remarks>The epoch is December 30, 0 (Gregorian).</remarks>

	const int epoch = -1; // 30. 12. 0 Gregorian



	/// <summary>The enumeration defines the months of the Julian

	/// calendar.

	/// </summary>

	public enum Month {

		/// <summary>

		/// January.

		/// </summary>

		january = 1,

		/// <summary>

		/// February.

		/// </summary>

		february,

		/// <summary>

		/// March.

		/// </summary>

		march,

		/// <summary>

		/// April.

		/// </summary>

		april,

		/// <summary>

		/// May.

		/// </summary>

		may,

		/// <summary>

		/// June.

		/// </summary>

		june,

		/// <summary>

		/// July.

		/// </summary>

		july,

		/// <summary>

		/// August.

		/// </summary>

		august,

		/// <summary>

		/// September.

		/// </summary>

		september,

		/// <summary>

		/// October.

		/// </summary>

		october,

		/// <summary>

		/// November.

		/// </summary>

		november,

		/// <summary>

		/// December.

		/// </summary>

		december

	};



	/// <summary>

	/// The method tells whether the year is a leap year.

	/// </summary>

	/// <param name="year">An integer representing the Julian year.

	/// </param>

	/// <returns>A boolean which is true if <paramref name="year"/> is

	/// a leap year.

	/// </returns>

	public static bool is_leap_year(int year) {

		return CCMath.mod(year, 4) == (year > 0 ? 0 : 3);

	}



	/// <summary>

	/// The method returns the fixed day number of the given Julian

	/// date.

	/// </summary>

	/// <param name="day">An integer representing the day of the month,

	/// counting from 1.

	/// </param>

	/// <param name="month">An integer representing the month in the

	/// Julian year.

	/// </param>

	/// <param name="year">An integer representing the Julian year.

	/// Positive and Negative values are allowed.

	/// </param>

	/// <returns>An integer value representing the fixed day number.

	/// </returns>

	public static int fixed_from_dmy(int day, int month, int year) {

		int y = year < 0 ? year+1 : year;

		int k = epoch - 1;

		k += 365 * (y-1);

		k += CCMath.div(y-1, 4);

		k += CCMath.div(367*month-362, 12);

		if (month > 2) {

			k += is_leap_year(year) ? -1 : -2;

		}

		k += day;



		return k;

	}



	/// <summary>

	/// The method computes the Julian year from a fixed day number.

	/// </summary>

	/// <param name="date">The fixed day number.

	/// </param>

	/// <returns>An integer value giving the Julian year of the date.

	/// </returns>

	public static int year_from_fixed(int date) {

		int approx = CCMath.div(4*(date-epoch)+1464, 1461);

		return approx <= 0 ? approx - 1 : approx;

	}



	/// <summary>

	/// The method computes the Julian year and month from a fixed day

	/// number.

	/// </summary>

	/// <param name="month">The output value giving the Julian month.

	/// </param>

	/// <param name="year">The output value giving the Julian year.

	/// </param>

	/// <param name="date">An integer value specifying the fixed day

	/// number.</param>

	public static void my_from_fixed(out int month, out int year, int date)

	{

		year = year_from_fixed(date);



		int prior_days = date - fixed_from_dmy(1, (int)Month.january,

			year);

		

		int correction;

		if (date < fixed_from_dmy(1, (int)Month.march, year)) {

			correction = 0;

		} else if (is_leap_year(year)) {

			correction = 1;

		} else {

			correction = 2;

		}



		month = CCMath.div(12 * (prior_days + correction) + 373, 367);

	}

	



	/// <summary>

	/// The method computes the Julian year, month, and day from a

	/// fixed day number.

	/// </summary>

	/// <param name="day">The output value returning the day of the

	/// month.

	/// </param>

	/// <param name="month">The output value giving the Julian month.

	/// </param>

	/// <param name="year">The output value giving the Julian year.

	/// </param>

	/// <param name="date">An integer value specifying the fixed day

	/// number.</param>

	public static void dmy_from_fixed(out int day, out int month,

		out int year, int date)

	{

		my_from_fixed(out month, out year, date);

		day = date - fixed_from_dmy(1, month, year) + 1;

	}



	/// <summary>A method computing the Julian month from a fixed

	/// day number.

	/// </summary>

	/// <param name="date">An integer specifying the fixed day number.

	/// </param>

	/// <returns>An integer value representing the Julian month.

	/// </returns>

	public static int month_from_fixed(int date) {

		int month, year;



		my_from_fixed(out month, out year, date);

		return month;

	}



	/// <summary>

	/// A method computing the day of the month from a fixed day number.

	/// </summary>

	/// <param name="date">An integer specifying the fixed day number.

	/// </param>

	/// <returns>An integer value representing the day of the month.

	/// </returns>

	public static int day_from_fixed(int date) {

		int day;

		int month;

		int year;



		dmy_from_fixed(out day, out month, out year, date);

		return day;

	}



	/// <summary>

	/// The method computes the difference between two Julian dates.

	/// </summary>

	/// <param name="dayA">The integer parameter gives the day of month

	/// of the first date.

	/// </param>

	/// <param name="monthA">The integer parameter gives the Julian

	/// month of the first date.

	/// </param>

	/// <param name="yearA">The integer parameter gives the Julian

	/// year of the first date.

	/// </param>

	/// <param name="dayB">The integer parameter gives the day of month

	/// of the second date.

	/// </param>

	/// <param name="monthB">The integer parameter gives the Julian

	/// month of the second date.

	/// </param>

	/// <param name="yearB">The integer parameter gives the Julian

	/// year of the second date.

	/// </param>

	/// <returns>An integer giving the difference of days from the first

	/// the second date.

	/// </returns>

	public static int date_difference(int dayA, int monthA, int yearA,

		int dayB, int monthB, int yearB)

	{

		return	fixed_from_dmy(dayB, monthB, yearB) -

			fixed_from_dmy(dayA, monthA, yearA);

	}



	/// <summary>

	/// The method computes the number of the day in the year from

	/// a Julian date.

	/// </summary>

	/// <param name="day">An integer representing the day of the month,

	/// counting from 1.

	/// </param>

	/// <param name="month">An integer representing the month in the

	/// Julian year.

	/// </param>

	/// <param name="year">An integer representing the Julian year.

	/// Negative values are allowed also.

	/// </param>

	/// <returns>An integer value giving the number of the day in the

	/// Julian year, counting from 1.

	/// </returns>

	public static int day_number(int day, int month, int year) {

		return date_difference(31, (int)Month.december, year-1,

			day, month, year);

	}



	/// <summary>

	/// The method computes the days remaining in the given Julian

	/// year from a Julian date.

	/// </summary>

	/// <param name="day">An integer representing the day of the month,

	/// counting from 1.

	/// </param>

	/// <param name="month">An integer representing the month in the

	/// Julian year.

	/// </param>

	/// <param name="year">An integer representing the Julian year.

	/// Negative values are allowed also.

	/// </param>

	/// <returns>An integer value giving the number of days remaining in

	/// the Julian year.

	/// </returns>

	public static int days_remaining(int day, int month, int year) {

		return date_difference(day, month, year,

			31, (int)Month.december, year);

	}

} // class CCJulianCalendar



/// <summary>

/// A class encapsulating the functions of the Hebrew calendar as static

/// methods.

/// </summary>

/// <remarks>

/// <para>

/// This class is not compatible to

/// <see cref="T:System.Globalization.HebrewCalendar"/>.

/// </para>

/// <seealso cref="T:CCFixed"/>

/// </remarks>

internal class CCHebrewCalendar {

	/// <summary>An integer defining the epoch of the Hebrew calendar

	/// as fixed day number.</summary>

	/// <remarks>The epoch is October 10, 3761 B.C.E. (Julian).</remarks>

	const int epoch = -1373427;



	/// <summary>The enumeration defines the months of the Gregorian

	/// calendar.

	/// </summary>

	/// <remarks>

	/// The enumaration differs from .NET which defines Tishri as month 1.

	/// </remarks>

	public enum Month {

		/// <summary>

		/// Nisan.

		/// </summary>

		nisan	 = 1,

		/// <summary>

		/// Iyyar.

		/// </summary>

		iyyar,

		/// <summary>

		/// Sivan.

		/// </summary>

		sivan,

		/// <summary>

		/// Tammuz.

		/// </summary>

		tammuz,

		/// <summary>

		/// Av.

		/// </summary>

		av,

		/// <summary>

		/// Elul.

		/// </summary>

		elul,

		/// <summary>

		/// Tishri.

		/// </summary>

		tishri,

		/// <summary>

		/// Heshvan.

		/// </summary>

		heshvan,

		/// <summary>

		/// Kislev.

		/// </summary>

		kislev,

		/// <summary>

		/// Teveth.

		/// </summary>

		teveth,

		/// <summary>

		/// Shevat.

		/// </summary>

		shevat,

		/// <summary>

		/// Adar.

		/// </summary>

		adar,

		/// <summary>

		/// Adar I. Only in years with Adar II.

		/// </summary>

		adar_I = 12,

		/// <summary>

		/// Adar II. Only in years wirh Adar I.

		/// </summary>

		adar_II = 13,

	};



	/// <summary>

	/// The method tells whether the year is a leap year.

	/// </summary>

	/// <param name="year">An integer representing the Hebrew year.

	/// </param>

	/// <returns>A boolean which is true if <paramref name="year"/> is

	/// a leap year.

	/// </returns>

	public static bool is_leap_year(int year) {

		return CCMath.mod(7*year+1, 19) < 7; 

	}



	/// <summary>

	/// The Method gives the number of the last month in a year, which

	/// is equal with the number of month in a Hebrew year.

	/// </summary>

	/// <param name="year">An integer representing the Hebrew year.

	/// </param>

	/// <returns>An integer giving the number of the last month of the 

	/// Hebrew year, which is the same as the numbers of month in the

	/// year.

	/// </returns>

	public static int last_month_of_year(int year) {

		return is_leap_year(year) ? 13 : 12;

	}



	

	/// <summary>The method is a helper function.</summary>

	/// <param name="year">An integer specifying the Hebrew year.

	/// </param>

	/// <returns>An integer representing the number of elapsed days

	/// until the Hebrew year.</returns>

	public static int elapsed_days(int year) {

		int months_elapsed = CCMath.div(235*year-234, 19);

		int r;

		int d = CCMath.div_mod(out r, months_elapsed, 1080);

		int parts_elapsed = 204 + 793 * r;

		int hours_elapsed = 11 + 12 * months_elapsed +

				    793 * d + CCMath.div(parts_elapsed, 1080);



		int day = 29*months_elapsed + CCMath.div(hours_elapsed, 24);



		if (CCMath.mod(3*(day+1), 7) < 3) {

			day += 1;

		}



		return day;

	}



	/// <summary>A method computing the delay of new year for the given

	/// Hebrew year.

	/// </summary>

	/// <param name="year">An integer that gives the Hebrew year.

	/// </param>

	/// <returns>The new year delay in days of the given Hebrew year.

	/// </returns>

	public static int new_year_delay(int year) {

		int ny1 = elapsed_days(year);

		int ny2 = elapsed_days(year+1);



		if (ny2 - ny1 == 356) {

			return 2;

		}

		int ny0 = elapsed_days(year-1);

		if (ny1 - ny0 == 382) {

			return 1;

		}

		return 0;

	}



	/// <summary>

	/// The method computes the last day of month (nummer of days in a

	/// month) of the given Hebrew year.

	/// </summary>

	/// <param name="month">The Hebrew month, allowed value between

	/// One and Thirteen.

	/// </param>

	/// <param name="year">An integer that gives the Hebrew year.

	/// </param>

	/// <returns>The number of the last day of the month of the given

	/// Hebrew year, which gives automatically the number of days in the

	/// month.

	/// </returns>

	/// <exception cref="T:System.ArgumentOutOfRange.Exception">

	/// The exception is thrown if month not between One and Thirteen.

	/// </exception>

	public static int last_day_of_month(int month, int year) {

		if (month < 1 || month > 13)

			throw new System.ArgumentOutOfRangeException("month",

				"Month should be between One and Thirteen.");

		switch (month) {

			case 2: return 29;

			case 4: return 29;

			case 6: return 29;

			case 8:

				if (!long_heshvan(year))

					return 29;

				break;

			case 9:

				if (short_kislev(year))

					return 29;

				break;

			case 10: return 29;

			case 12:

				if (!is_leap_year(year))

					return 29;

				break;

			case 13: return 29;

		}

		return 30;

	}

	

	/// <summary>

	/// The functions checks whether the month Heshvan is a long one

	/// in the given Hebrew year.

	/// </summary>

	/// <param name="year">An integer that gives the Hebrew year.

	/// </param>

	/// <returns>A boolean value: true if there is a long Heshvan

	/// in the given Hebrew year; false otherwise.

	/// </returns>

	public static bool long_heshvan(int year) {

		return CCMath.mod(days_in_year(year), 10) == 5;

	}



	/// <summary>

	/// The functions checks whether the month Kislev is a short one

	/// in the given Hebrew year.

	/// </summary>

	/// <param name="year">An integer that gives the Hebrew year.

	/// </param>

	/// <returns>A boolean value: true if there is a short Kislev

	/// in the given Hebrew year; false otherwise.

	/// </returns>

	public static bool short_kislev(int year) {

		return CCMath.mod(days_in_year(year), 10) == 3;

	}



	/// <summary>

	/// The functions gives the number of days in the specified Hebrew

	/// year.

	/// </summary>

	/// <param name="year">An integer that gives the Hebrew year.

	/// </param>

	/// <returns>The days of the Hebrew year as integer.

	/// </returns>

	public static int days_in_year(int year) {

		return	fixed_from_dmy(1, 7, year+1) -

			fixed_from_dmy(1, 7, year);

	}



	/// <summary>

	/// The method returns the fixed day number of the given Hebrew

	/// date.

	/// </summary>

	/// <param name="day">An integer representing the day of the month,

	/// counting from 1.

	/// </param>

	/// <param name="month">An integer representing the month in the

	/// Hebrew year.

	/// </param>

	/// <param name="year">An integer representing the Hebrew year.

	/// Non-positive values are allowed also.

	/// </param>

	/// <returns>An integer value representing the fixed day number.

	/// </returns>

	public static int fixed_from_dmy(int day, int month, int year) {

		int m;

		int k = epoch-1;

		k += elapsed_days(year);

		k += new_year_delay(year);



		if (month < 7) {

			int l = last_month_of_year(year);

			for (m = 7; m <= l; m++) {

				k += last_day_of_month(m, year);

			}

			for (m = 1; m < month; m++) {

				k += last_day_of_month(m, year);

			}

		}

		else {

			for (m = 7; m < month; m++) {

				k += last_day_of_month(m, year);

			}

		}

		

		k += day;



		return k;

	}



	/// <summary>

	/// The method computes the Hebrew year from a fixed day number.

	/// </summary>

	/// <param name="date">The fixed day number.

	/// </param>

	/// <returns>An integer value giving the Hebrew year of the date.

	/// </returns>

	public static int year_from_fixed(int date) {

		int approx = (int)System.Math.Floor(

			((double)(date - epoch))/(35975351.0/98496.0));

		int y;

		for (y = approx; date >= fixed_from_dmy(1, 7, y); y++) {} 

		return y-1;

	}



	/// <summary>

	/// The method computes the Hebrew year and month from a fixed day

	/// number.

	/// </summary>

	/// <param name="month">The output value giving the Hebrew month.

	/// </param>

	/// <param name="year">The output value giving the Hebrew year.

	/// </param>

	/// <param name="date">An integer value specifying the fixed day

	/// number.</param>

	public static void my_from_fixed(out int month, out int year,

		int date)

	{

		year = year_from_fixed(date);



		int start = date < fixed_from_dmy(1, 1, year) ? 7 : 1;



		for (month = start;

		     date > fixed_from_dmy(last_day_of_month(month, year),

		     				month, year);

		     month++)

		{}

	}



	/// <summary>

	/// The method computes the Hebrew year, month, and day from a

	/// fixed day number.

	/// </summary>

	/// <param name="day">The output value returning the day of the

	/// month.

	/// </param>

	/// <param name="month">The output value giving the Hebrew month.

	/// </param>

	/// <param name="year">The output value giving the Hebrew year.

	/// </param>

	/// <param name="date">An integer value specifying the fixed day

	/// number.</param>

	public static void dmy_from_fixed(out int day, out int month,

		out int year, int date)

	{

		my_from_fixed(out month, out year, date);

		day = date - fixed_from_dmy(1, month, year) + 1;

	}



	/// <summary>A method computing the Hebrew month from a fixed

	/// day number.

	/// </summary>

	/// <param name="date">An integer specifying the fixed day number.

	/// </param>

	/// <returns>An integer value representing the Hebrew month.

	/// </returns>

	public static int month_from_fixed(int date) {

		int month, year;



		my_from_fixed(out month, out year, date);

		return month;

	}



	/// <summary>

	/// A method computing the day of the month from a fixed day number.

	/// </summary>

	/// <param name="date">An integer specifying the fixed day number.

	/// </param>

	/// <returns>An integer value representing the day of the month.

	/// </returns>

	public static int day_from_fixed(int date) {

		int day, month, year;

		

		dmy_from_fixed(out day, out month, out year, date);

		return day;

	}



	/// <summary>

	/// The method computes the difference between two Hebrew dates.

	/// </summary>

	/// <param name="dayA">The integer parameter gives the day of month

	/// of the first date.

	/// </param>

	/// <param name="monthA">The integer parameter gives the Hebrew

	/// month of the first date.

	/// </param>

	/// <param name="yearA">The integer parameter gives the Hebrew

	/// year of the first date.

	/// </param>

	/// <param name="dayB">The integer parameter gives the day of month

	/// of the second date.

	/// </param>

	/// <param name="monthB">The integer parameter gives the Hebrew

	/// month of the second date.

	/// </param>

	/// <param name="yearB">The integer parameter gives the Hebrew

	/// year of the second date.

	/// </param>

	/// <returns>An integer giving the difference of days from the first

	/// the second date.

	/// </returns>

	public static int date_difference(int dayA, int monthA, int yearA,

		int dayB, int monthB, int yearB)

	{

		return	fixed_from_dmy(dayB, monthB, yearB) -

			fixed_from_dmy(dayA, monthA, yearA);

	}



	/// <summary>

	/// The method computes the number of the day in the year from

	/// a Hebrew date.

	/// </summary>

	/// <param name="day">An integer representing the day of the month,

	/// counting from 1.

	/// </param>

	/// <param name="month">An integer representing the month in the

	/// Hebrew year.

	/// </param>

	/// <param name="year">An integer representing the Hebrew year.

	/// </param>

	/// <returns>An integer value giving the number of the day in the

	/// Hebrew year, counting from 1.

	/// </returns>

	public static int day_number(int day, int month, int year) {

		return date_difference(1, 7, year,

			day, month, year) + 1;

	}



	/// <summary>

	/// The method computes the days remaining in the given Hebrew

	/// year from a Hebrew date.

	/// </summary>

	/// <param name="day">An integer representing the day of the month,

	/// counting from 1.

	/// </param>

	/// <param name="month">An integer representing the month in the

	/// Hebrew year.

	/// </param>

	/// <param name="year">An integer representing the Hebrew year.

	/// </param>

	/// <returns>An integer value giving the number of days remaining in

	/// the Hebrew year.

	/// </returns>

	public static int days_remaining(int day, int month, int year) {

		return date_difference(day, month, year,

			1, 7, year+1)-1;

	}

} // class HebrewCalendar





/// <summary>

/// A class encapsulating the functions of the Islamic calendar as static

/// methods.

/// </summary>

/// <remarks>

/// <para>There is no difference here in using Hijri or Islamic calendar.

/// </para>

/// <para>The epoch of the Islamic calendar isn't fixed, because we cannot

/// surely say today, when the crescent of the new moon has been observed 

/// around the July 16, 622 C.E. Julian. Even today the start and end of 

/// the month Ramadan is defined by religous authorities. So the calendar

/// can be offset by two days.

/// </para> 

/// <para>

/// We don't support the offset here, however we changed the epoch from

/// "Calendrical Calculations" to value, that .Net seems to be using.

/// </para>

/// <para>

/// This class is not compatible to

/// <see cref="T:System.Globalization.HijriCalendar"/>.

/// </para>

/// <seealso cref="T:CCFixed"/>

/// </remarks>

internal class CCHijriCalendar {

	/// <summary>An integer defining the epoch of the Gregorian calendar

	/// as fixed day number.</summary>

	/// <remarks>

	/// <para>

	/// The epoch is given as 16 July 622 C.E. Julian (R.D. 227015)

	/// in Calendrical Calculations, the approximate date of

	/// the emigration of

	/// Muhammed to Medina. However there is no way to determine today

	/// the observation of the crescent of the new moon in July 622 C.E.

	/// (Julian). So there is some variability in the epoch.

	/// Religous authorities determine the epoch by observing the

	/// crescent of the new moon for the month Ramadan, so there might

	/// be an offsets by two days of the epoch.

	/// </para>

	/// <para>Windows

	/// supports an AddHijriDate parameter in the registry to adapt

	/// for it. It seems that the .NET implementation of

	/// HijriCalendar uses an epoch of 227014, so we use it here. The

	/// ArgumentOutOfRangeException gives July, 18 622 as epoch,

	/// which is 227014 supporting our theory.

	/// </para>

	/// </remarks>

	const int epoch = 227014;



	/// <summary>The enumeration defines the months of the Islamic

	/// calendar.

	/// </summary>

	public enum Month {

		/// <summary>

		/// Muharram.

		/// </summary>

		muharram = 1,

		/// <summary>

		/// Safar.

		/// </summary>

		safar,

		/// <summary>

		/// Rabi I.

		/// </summary>

		rabi_I,

		/// <summary>

		/// Rabi II.

		/// </summary>

		rabi_II,

		/// <summary>

		/// Jumada I.

		/// </summary>

		jumada_I,

		/// <summary>

		/// Jumada II.

		/// </summary>…

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