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librock_french_calendar - French republican serial day number conversions (Scott E. Lee's sdncal library)
#License - #Source code - #Example Use -


#include <librock/sdncalh.h>

        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
          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 *librock_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.


 /* 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.
 * 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 ...


 *     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.


 *     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.)


 *     This algorithm has been tested from the year 1 to 14.  The source
 *     code of the verification program is included in the sdncal package.


 *     I have found no detailed, authoritative reference on this calendar.
 *     The algorithms are based on a preponderance of less authoritative
 *     sources.


  //No external calls


  Copyright 1993-1995, Scott E. Lee, all rights reserved.
  Licensed under BSD-ish license, NO WARRANTY. Copies must retain this block.
  License text in <librock/license/sdncal.txt> librock_LIDESC_HC=553e181388455f0eef17ccd9e2a51c1f3ae8daf0

Source Code

./acquired/sdncal/sdnfrnch.c (implementation, plus source of this manual page)

This software is part of Librock

Rapid reuse, without rework. Details
This page copyright (C) 2002-2003 Forrest J. Cavalier III, d-b-a Mib Software, Saylorsburg PA 18353, USA

Verbatim copying and distribution of this generated page is permitted in any medium provided that no changes are made.
(The source of this manual page may be covered by a more permissive license which allows modifications.)

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