The clarification of the difference between G2H and and h_date (Documentation)

[sam-ka]

Hello everyone.

I'm trying to use ITL to convert Gregorian dates to their Hijri counterparts. Looking at hijri.h, the header defines two different functions that seem to do what I want. Perplexingly though, these two functions yield different results: Running demo_hijri.c on my system gives 23/8 for h_date and 24/8 for G2H.

What is the difference between these two functions? and which of these two functions should application developers use to convert Gregorian dates?

hijri.h should probably include a description of these differences as well.

[aelmahmoudy]

h_date, g_date defined in hijri.c, according to code comments in hijri.c:

• (*)NOTE: A great deal of inspiration as well as algorithmic insight was
• based on the lisp code from GNU Emacs' cal-islam.el which itself
• is baed on ``Calendrical Calculations'' by Nachum Dershowitz and
• Edward M. Reingold.

H2G,G2H defined in umm_alqura.c, according to code comments in umm_alqura.c:

• This is a program that computes the Hijary dates for Umm-AlQura
• calendar the official calendar of the Kingdom of Saudi Arabia.