convert o exact arabic date

[mohammed ragab abdelnaeim]

i want to get the accurate arabic date(hijrah date) when user enter greogian date or inverse, i reached a solution but some times return one day difference about real date.
function i use nls_calendar

[Ian Parker]

That's an interesting question. Where is the function nls_calendar from? Did you write it?

As far as I understand the Arabic date system, it depends on the lunar cycle and weather. Or is that only for determining eid and other religious occasions?

How deterministic is it? Like, is there a single algorithm that will do the job or must a person use a lookup table for every conceivable date relevant to the app?

Surely this sort of thing must have been fully solved before?