Leap Year Issue: Incorrect Dates from Farvardin 1, 1404

[zanjani99]

I have encountered an issue with the jcal library regarding leap year handling. The current year, 1404 in the Jalali calendar, is a leap year. However, it appears that jcal does not account for this, resulting in incorrect dates starting from Farvardin 1, 1404

[pouyanh]

Due to #16 we must switch to the fork and follow up this issue on persiancal#14

[ilius]

I don't know if the correct algorithm has been announced by the government, but the 33-year algorithm is simple, and it matches the official calendar so far.

This is the entire code for jalali_is_jleap:

int jalali_is_jleap(int year)
{
	int jy = year - 979;
	int jyd = jy / 33;
	int jym = jy % 33;
	int jyd2 = (jy+1) / 33;
	int jym2 = (jy+1) % 33;
	if (1 == (jyd2-jyd)*8+(jym2+3)/4-(jym+3)/4) {
		return 1;
	}
	return 0;
}

I have created this fork that use this code to fix the issue.

BTW I have set this algorithm by default in starcal since 2008, and never had a mismatch with Persian calendar.

Also here is the Go implementation, with tests:
https://github.com/ilius/libgostarcal/tree/master/cal_types/jalali