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 from January 1st, 4713 B.C. 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 Julian Day Count, visit
http://www.hermetic.ch/cal_stud/jdn.htm. For more
information on calendar systems visit http://www.boogle.com/info/cal-overview.html. Excerpts from this page are
included in these instructions, and are in quotes.
The constants below are defined by this extension, and
will only be available when the extension has either
been compiled into PHP or dynamically loaded at runtime.