Islamic Calendar

Mon, 27 Jun 2016 12:32:48 GMT

AIUI the Islamic calendar is purely lunar. ie. the year is a fixed number of lunar months, and the seasons drift round the year, unlike a solar calendar (Gregorian) or lunisolar (Jewish, Chinese (?)).

Traditionally, a month starts when you first see the new moon. However, with astronomical calculation, it's easy to predict what day you are GOING to see the moon (provided it's not cloudy). There's also an understanding that after thirty days you move on to the next month anyway, so even if you follow the traditional system, the months never *accumulate* errors, there's always one month per new moon, and if one starts a bit late, it's correspondingly shorter.

In particular, this Ramadan, for many people following the traditional system, it started one day late, but it finishes a day late at random other years, not particularly the same year it started late, so it's likely everyone will celebrate finishing at the same time.

What I could NOT find in a quick google was which countries used which calendar in practice, for civil use (Gregorian or an astronomical version of the Islamic calendar? usually not an observation-based Islamic calendar?) and which countries' tradition used which calendar for religious festivals (astronomical calendar? observation calendar)? I'd assumed that would be fairly obvious, anyone able to fill me in?

This came about, because someone was complaining that in order to get timezone code correct, you had to take into account that Egypt cancelled daylight saving during ramadan. But I don't know what calendar they actually used for that.

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jack

Islamic Calendar