/* $selId: french.c,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. */ /************************************************************************** * * These are the externally visible components of this file: * * void * SdnToFrench( * long int sdn, * int *pYear, * int *pMonth, * int *pDay); * * Convert a SDN to a French republican calendar date. If the input SDN is * before the first day of year 1 or after the last day of year 14, the * three output values will all be set to zero, otherwise *pYear will be in * the range 1 to 14 inclusive; *pMonth will be in the range 1 to 13 * inclusive; *pDay will be in the range 1 to 30 inclusive. If *pMonth is * 13, the SDN represents one of the holidays at the end of the year and * *pDay will be in the range 1 to 6 inclusive. * * long int * FrenchToSdn( * int year, * int month, * int day); * * Convert a French republican calendar date to a SDN. Zero is returned * when the input date is detected as invalid or out of the supported * range. The return value will be > 0 for all valid, supported dates, but * there are some invalid dates that will return a positive value. To * verify that a date is valid, convert it to SDN and then back and compare * with the original. * * char *FrenchMonthName[14]; * * Convert a French republican month number (1 to 13) to the name of the * French republican month (null terminated). An index of 13 (for the * "extra" days at the end of the year) will return the string "Extra". An * index of zero will return a zero length string. * * VALID RANGE * * These routines only convert dates in years 1 through 14 (Gregorian * dates 22 September 1792 through 22 September 1806). This more than * covers the period when the calendar was in use. * * I would support a wider range of dates, but I have not been able to * find an authoritative definition of when leap years were to have * occurred. There are suggestions that it was to skip a leap year ever * 100 years like the Gregorian calendar. * * CALENDAR OVERVIEW * * The French republican calendar was adopted in October 1793 during * the French Revolution and was abandoned in January 1806. The intent * was to create a new calendar system that was based on scientific * principals, not religious traditions. * * The year is divided into 12 months of 30 days each. The remaining 5 * to 6 days in the year are grouped at the end and are holidays. Each * month is divided into three decades (instead of weeks) of 10 days * each. * * The epoch (first day of the first year) is 22 September 1792 in the * Gregorian calendar. Leap years are every fourth year (year 3, 7, * 11, etc.) * * TESTING * * This algorithm has been tested from the year 1 to 14. The source * code of the verification program is included in this package. * * REFERENCES * * I have found no detailed, authoritative reference on this calendar. * The algorithms are based on a preponderance of less authoritative * sources. * **************************************************************************/ #include "sdncal.h" #define FRENCH_SDN_OFFSET 2375474 #define DAYS_PER_4_YEARS 1461 #define DAYS_PER_MONTH 30 #define FIRST_VALID 2375840 #define LAST_VALID 2380952 void SdnToFrench( long int sdn, int *pYear, int *pMonth, int *pDay) { long int temp; int dayOfYear; if (sdn < FIRST_VALID || sdn > LAST_VALID) { *pYear = 0; *pMonth = 0; *pDay = 0; return; } temp = (sdn - FRENCH_SDN_OFFSET) * 4 - 1; *pYear = temp / DAYS_PER_4_YEARS; dayOfYear = (temp % DAYS_PER_4_YEARS) / 4; *pMonth = dayOfYear / DAYS_PER_MONTH + 1; *pDay = dayOfYear % DAYS_PER_MONTH + 1; } long int FrenchToSdn( int year, int month, int day) { /* check for invalid dates */ if (year < 1 || year > 14 || month < 1 || month > 13 || day < 1 || day > 30) { return (0); } return ((year * DAYS_PER_4_YEARS) / 4 + (month - 1) * DAYS_PER_MONTH + day + FRENCH_SDN_OFFSET); } char *FrenchMonthName[14] = { "", "Vendemiaire", "Brumaire", "Frimaire", "Nivose", "Pluviose", "Ventose", "Germinal", "Floreal", "Prairial", "Messidor", "Thermidor", "Fructidor", "Extra" }; /* * Local variables: * tab-width: 4 * c-basic-offset: 4 * End: * vim600: sw=4 ts=4 fdm=marker * vim<600: sw=4 ts=4 */