#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]; extern char *JewishMonthHebName[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 */