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97 lines
3.8 KiB
C
97 lines
3.8 KiB
C
#ifndef _INCLUDED_SDNCAL_H
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#define _INCLUDED_SDNCAL_H
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/*
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* This code has been modified for use with PHP
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* by Shane Caraveo shane@caraveo.com
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* see below for more details
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*
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*/
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/* $selId: sdncal.h,v 2.0 1995/10/24 01:13:06 lees Exp $
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* Copyright 1993-1995, Scott E. Lee, all rights reserved.
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* Permission granted to use, copy, modify, distribute and sell so long as
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* the above copyright and this permission statement are retained in all
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* copies. THERE IS NO WARRANTY - USE AT YOUR OWN RISK.
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*/
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/**************************************************************************
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*
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* This package defines a set of routines that convert calendar dates to
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* and from a serial day number (SDN). The SDN is a serial numbering of
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* days where SDN 1 is November 25, 4714 BC in the Gregorian calendar and
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* SDN 2447893 is January 1, 1990. This system of day numbering is
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* sometimes referred to as Julian days, but to avoid confusion with the
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* Julian calendar, it is referred to as serial day numbers here. The term
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* Julian days is also used to mean the number of days since the beginning
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* of the current year.
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*
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* The SDN can be used as an intermediate step in converting from one
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* calendar system to another (such as Gregorian to Jewish). It can also
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* be used for date computations such as easily comparing two dates,
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* determining the day of the week, finding the date of yesterday or
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* calculating the number of days between two dates.
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*
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* When using this software on 16 bit systems, be careful to store SDNs in
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* a long int, because it will not fit in the 16 bits that some systems
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* allocate to an int.
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*
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* For each calendar, there are two routines provided. One converts dates
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* in that calendar to SDN and the other converts SDN to calendar dates.
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* The routines are named SdnTo<CALENDAR>() and <CALENDAR>ToSdn(), where
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* <CALENDAR> is the name of the calendar system.
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*
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* SDN values less than one are not supported. If a conversion routine
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* returns an SDN of zero, this means that the date given is either invalid
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* or is outside the supported range for that calendar.
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*
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* At least some validity checks are performed on input dates. For
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* example, a negative month number will result in the return of zero for
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* the SDN. A returned SDN greater than one does not necessarily mean that
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* the input date was valid. To determine if the date is valid, convert it
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* to SDN, and if the SDN is greater than zero, convert it back to a date
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* and compare to the original. For example:
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*
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* int y1, m1, d1;
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* int y2, m2, d2;
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* long int sdn;
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* ...
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* sdn = GregorianToSdn(y1, m1, d1);
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* if (sdn > 0) {
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* SdnToGregorian(sdn, &y2, &m2, &d2);
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* if (y1 == y2 && m1 == m2 && d1 == d2) {
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* ... date is valid ...
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* }
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* }
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*
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**************************************************************************/
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/* Gregorian calendar conversions. */
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void SdnToGregorian(long int sdn, int *pYear, int *pMonth, int *pDay);
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long int GregorianToSdn(int year, int month, int day);
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extern char *MonthNameShort[13];
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extern char *MonthNameLong[13];
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/* Julian calendar conversions. */
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void SdnToJulian(long int sdn, int *pYear, int *pMonth, int *pDay);
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long int JulianToSdn(int year, int month, int day);
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/* Jewish calendar conversions. */
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void SdnToJewish(long int sdn, int *pYear, int *pMonth, int *pDay);
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long int JewishToSdn(int year, int month, int day);
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extern char *JewishMonthName[14];
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/* French republic calendar conversions. */
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void SdnToFrench(long int sdn, int *pYear, int *pMonth, int *pDay);
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long int FrenchToSdn(int inputYear, int inputMonth, int inputDay);
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extern char *FrenchMonthName[14];
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/* Islamic calendar conversions. */
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/* Not implemented yet. */
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/* Day of week conversion. 0=Sunday, 6=Saturday */
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int DayOfWeek(long int sdn);
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extern char *DayNameShort[7];
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extern char *DayNameLong[7];
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#endif /* _INCLUDED_SDNCAL_H */
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