Calendar manipulation routines from Scott E. Lee.

[gedcom-parse.git] / gedcom / calendar / french.c

diff --git a/gedcom/calendar/french.c b/gedcom/calendar/french.c
new file mode 100644 (file)
index 0000000..e4452fe
--- /dev/null
+++ b/gedcom/calendar/french.c
@@ -0,0 +1,160 @@
+/* This file is taken from http://www.genealogy.org/~scottlee/
+   Only this initial comment has been added.  The next comment
+   gives the original copyright notice.
+*/
+
+
+/* $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 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 - 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
+           + SDN_OFFSET );
+}
+
+char *FrenchMonthName[14] = {
+    "",
+    "Vendemiaire",
+    "Brumaire",
+    "Frimaire",
+    "Nivose",
+    "Pluviose",
+    "Ventose",
+    "Germinal",
+    "Floreal",
+    "Prairial",
+    "Messidor",
+    "Thermidor",
+    "Fructidor",
+    "Extra"
+};