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/* $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
*/
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