Jalali calendar is a small and portable free software library to manipulate date and time in Jalali calendar system. It's written in C and has absolutely zero dependencies. It works on top of any POSIX.1-2001 (and later) compatible libc implementations. Jalali calendar provides an API similar to that of libc's timezone, date and time functions.
Jalali calendar package consists of a library namely libjalali and two simple and easy to use terminal tools, jcal and jdate with functionality similar to UNIX cal and date.