Convert gregorian Date to Hijri Date

Calendar arithmetic is extremly complex.

Oracle JET is not the tool to provide calendar arithemtic (afaik) - of cause you might want to integrate some other js-framework that can do it.

I suggest to use something that already has a good implementation. For example you can ask any oracle database to use a date and to prettyprint this date using the Gregorian or one Islamic calendar.

Here is an example:

alter session set nls_calendar = 'Gregorian';select to_char(sysdate) today_gregorian from dual;19-07-2019alter session set nls_calendar = 'English Hijrah';select to_char(sysdate) today_islamic from dual;16 Thoul Ki'Dah  1440alter session set nls_calendar = 'Arabic Hijrah';select to_char(sysdate) today_islamic from dual;16 ذو القعدة 1440