1 #ifndef SDNCAL_H 2 #define SDNCAL_H 3 /* 4 * This code has been modified for use with PHP 5 * by Shane Caraveo shane@caraveo.com 6 * see below for more details 7 * 8 */ 9 10 /* $selId: sdncal.h,v 2.0 1995/10/24 01:13:06 lees Exp $ 11 * Copyright 1993-1995, Scott E. Lee, all rights reserved. 12 * Permission granted to use, copy, modify, distribute and sell so long as 13 * the above copyright and this permission statement are retained in all 14 * copies. THERE IS NO WARRANTY - USE AT YOUR OWN RISK. 15 */ 16 17 /************************************************************************** 18 * 19 * This package defines a set of routines that convert calendar dates to 20 * and from a serial day number (SDN). The SDN is a serial numbering of 21 * days where SDN 1 is November 25, 4714 BC in the Gregorian calendar and 22 * SDN 2447893 is January 1, 1990. This system of day numbering is 23 * sometimes referred to as Julian days, but to avoid confusion with the 24 * Julian calendar, it is referred to as serial day numbers here. The term 25 * Julian days is also used to mean the number of days since the beginning 26 * of the current year. 27 * 28 * The SDN can be used as an intermediate step in converting from one 29 * calendar system to another (such as Gregorian to Jewish). It can also 30 * be used for date computations such as easily comparing two dates, 31 * determining the day of the week, finding the date of yesterday or 32 * calculating the number of days between two dates. 33 * 34 * When using this software on 16 bit systems, be careful to store SDNs in 35 * a long int, because it will not fit in the 16 bits that some systems 36 * allocate to an int. 37 * 38 * For each calendar, there are two routines provided. One converts dates 39 * in that calendar to SDN and the other converts SDN to calendar dates. 40 * The routines are named SdnTo<CALENDAR>() and <CALENDAR>ToSdn(), where 41 * <CALENDAR> is the name of the calendar system. 42 * 43 * SDN values less than one are not supported. If a conversion routine 44 * returns an SDN of zero, this means that the date given is either invalid 45 * or is outside the supported range for that calendar. 46 * 47 * At least some validity checks are performed on input dates. For 48 * example, a negative month number will result in the return of zero for 49 * the SDN. A returned SDN greater than one does not necessarily mean that 50 * the input date was valid. To determine if the date is valid, convert it 51 * to SDN, and if the SDN is greater than zero, convert it back to a date 52 * and compare to the original. For example: 53 * 54 * int y1, m1, d1; 55 * int y2, m2, d2; 56 * long int sdn; 57 * ... 58 * sdn = GregorianToSdn(y1, m1, d1); 59 * if (sdn > 0) { 60 * SdnToGregorian(sdn, &y2, &m2, &d2); 61 * if (y1 == y2 && m1 == m2 && d1 == d2) { 62 * ... date is valid ... 63 * } 64 * } 65 * 66 **************************************************************************/ 67 68 /* Gregorian calendar conversions. */ 69 void SdnToGregorian(long int sdn, int *pYear, int *pMonth, int *pDay); 70 long int GregorianToSdn(int year, int month, int day); 71 extern char *MonthNameShort[13]; 72 extern char *MonthNameLong[13]; 73 74 /* Julian calendar conversions. */ 75 void SdnToJulian(long int sdn, int *pYear, int *pMonth, int *pDay); 76 long int JulianToSdn(int year, int month, int day); 77 78 /* Jewish calendar conversions. */ 79 void SdnToJewish(long int sdn, int *pYear, int *pMonth, int *pDay); 80 long int JewishToSdn(int year, int month, int day); 81 extern char *JewishMonthName[14]; 82 extern char *JewishMonthNameLeap[14]; 83 extern char *JewishMonthHebName[14]; 84 extern char *JewishMonthHebNameLeap[14]; 85 extern int monthsPerYear[19]; 86 87 /* French republic calendar conversions. */ 88 void SdnToFrench(long int sdn, int *pYear, int *pMonth, int *pDay); 89 long int FrenchToSdn(int inputYear, int inputMonth, int inputDay); 90 extern char *FrenchMonthName[14]; 91 92 /* Islamic calendar conversions. */ 93 /* Not implemented yet. */ 94 95 /* Day of week conversion. 0=Sunday, 6=Saturday */ 96 int DayOfWeek(long int sdn); 97 extern char *DayNameShort[7]; 98 extern char *DayNameLong[7]; 99 100 #endif /* SDNCAL_H */ 101
