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 in PHP 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
