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