Wandering through the realms of the cosmos, pondering its huge vastness

Eid’l Fitr – An Astronomical Date

In the Philippines, September 10 was declared as a non-working holiday to give way for the celebration for the end of the Muslims’ holy month of fasting, the Ramadan.

Eid” is an Arabic word meaning “festivity” while “Fiṭr” means “to purify.” The holiday is thus a symbol of purification after completing the fasting month.

According to a fellow Filipino amateur astronomer, Eid’l Ftr has its own astronomical roots. Below was quoted from his original post.

I read about the Astronomical basis of the date of Eid’l Fitr and this is what I learned. To those more knowledgeable than me, please correct me if something here is wrong.

Eid’l Fitr marks the end of Ramadan, a whole month of fasting which starts on the first day of the 9th month of the Islamic calendar. Thus, Eid’l Fitr is celebrated every first day of the 10th month of the Islamic calendar.

The Islamic calendar (or the Hijri calendar) is based on the synodic month* and starts on a New Moon. It consists of 12 synodic months. As computed, it is 10 to 11 days shorter than the Gregorian calendar we widely use. Thus, Eid’l Fitr is celebrated 10 to 11 days earlier each year. Next year, it will be on the 31th of August.

*The synodic month is the period it takes the moon to reach the same exact phase. (e.g. one new moon to another new moon) It lasts for 29.531 days. Thus, 12 synodic months consists of 354.372 days.

Sometimes it’s also fun to learn the role of astronomy in several cultural practices of different societies. 😀

2 responses

  1. Michael

    Thanks for posting this. It’s quite fascinating, and prompted me to look up a bit more about Ramadan. I hadn’t realized that it was part of a true lunar calendar that is actually allowed to recess through the entire solar year over a period of time. I’m currently getting ready to write a paper about the calendar used by the Qumran Community (Dead Sea Scrolls), which was based upon an idealized solar year of 364 days. I’m wanting to research how they might have dealt with the roughly 30-hour discrepancy with the true solar year, and I guess I had a presumption that they couldn’t have simply allowed the dates to drift. But here’s a well-known modern example of a calendar that does just that! I guess I’ll just see what I learn about the Qumran calendar. Thanks again. Did you get any photos of the recent “celestial trio?” From my northerly locale I only captured Venus and the Moon.

    September 16, 2010 at 7:39 pm

    • Same here. We only saw the Moon and Venus during that night. Mars was too faint to be seen because of the cloudy sky.

      Clear skies on the International Observe the Moon Night! 🙂

      September 17, 2010 at 1:22 pm

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