Usayd Networks Forum

Asalamualikum | Peace be with you

Some people have had issues with the Hijri Date plugin/service being slightly inaccurate at times. This is an unfortunate but inevitable occurrence due to the maths required to calculate the Hijri Date, as explained by the original programmer.

These were taken from an email conversation where the issue was discussed:

"...whether you can product exact dates or not depends on whether you believe Islamic dates are based on the position of the moon (as can now be calculated), or whether it has to be based on sighting. It’s the same issue as whether or not you can calculate Eid etc. in advance and exactly, or whether if it is a requirement for a sighting...in the later it clearly isn’t possible."

And a small description of how the script works:

As you'll see from the comments, it's essentially a two step conversion first turning the Gregorian date (e.g. 20/05/2006) into a standard Julian day count (days since Jan 1st 4713BC) and then turning this into the Hijri date. I
don't claim to be an astronomer or fully follow how the algorithm works
(though sources are cited if you're interested in where the magic
numbers come from) so can't give you insight into the algorithms -- they
are 'off the shelf' and seem to all use the Julian day count which is a
common way to standardise across calendar systems.

Hope that helps a little