Calendars support in postgresql

You know that many calendars exist in the world such as Japanese, Indian,
Hebrew, Persian(jalali), ... and no support of these calendars are
supported in postgresql.

The only calendar that is supported in postgresql, is "Gregorian". there
is no support in glibc for calendars in localization support and they
don't have any plan for implementing it.

I wrote tow conversion function for converting between Gregorian and
Persian calendar dates:
gregorian2jalali(gregorian) and jalali2gregorian(jalali)

It is very useful for applications, so they insert date in the tables in
their calendar using this function and select the date in their calendar
using it.

This is useful, writing a function that convert between all calendars. I
am working on this function for some calendars.