Muslims praying.(eyelash/Flickr)

The Gregorian Calendar’s date for Yom Kippur varies every year, but because it always lasts for a 25-hour period (sundown to sundown, give or take), the fast always lasts the same amount of time. Not so for Muslims and their holiday of fasting, the holy month of Ramadan. Because the fast takes place solely during daylight hours (albeit for every day of a full month), the period of time during which an observant Muslim must go without food or drink can change depending on when in the year Ramadan falls. And because Ramadan can fall at any time of the solar year—depending on the moon, it falls back roughly 11 days each year—that means that some Ramadans are more difficult than other Ramadans.

A case in point in this year. Ramadan begins today and lasts through the 29th, and while the days won’t be as long as they will be, say, next year, or the year after that, we are definitely talking about going well over 12 hours without sustenance—for 30 straight days!

In an ecumenical spirit, here is some Yom Kippur fasting advice that our Muslim friends may find helpful (caffeine suppositories optional).

Related: Fast Food [Tablet Magazine]