V. Calendar functions

The calendar functions are only available if you have compiled the calendar extension in dl/calendar. Read dl/README for instructions on using it.

The calendar extension presents a series of functions to simplify converting between different calendar formats. The intermediary or standard it is based on is the Julian Day Count. The Julian Day Count is a count of days starting way earlier than any date most people would need to track (somewhere around 4000bc). To convert between calendar systems, you must first convert to Julian Day Count, then to the calendar system of your choice. Julian Day Count is very different from the Julian Calendar! For more information on calendar systems visit http://genealogy.org/~scottlee/cal-overview.html. Excerpts from this page are included in these instructions, and are in quotes.

Table of Contents
JDToGregorian — Converts Julian Day Count to Gregorian date
GregorianToJD — Converts a Gregorian date to Julian Day Count
JDToJulian — Converts a Julian Calendar date to Julian Day Count
JulianToJD — Converts a Julian Calendar date to Julian Day Count
JDToJewish — Converts a Julian Day Count to the Jewish Calendar
JewishToJD — Converts a date in the Jewish Calendar to Julian Day Count
JDToFrench — Converts a Julian Day Count to the French Republican Calendar
FrenchToJD — Converts a date from the French Republican Calendar to a Julian Day Count
JDMonthName — Returns a month name
JDDayOfWeek — Returns the day of the week
easter_date — get UNIX timestamp for midnight on Easter of a given year
easter_days — get number of days after March 21 on which Easter falls for a given year