Islam functions on a lunar calendar that doesn’t quite line up with the solar Gregorian calendar that the secular world uses. So while Muslim holidays are always the same day on the Muslim calendar, they happen on different days on the Gregorian calendar – typically moving 11 or 12 days earlier each year. In 2012, Ramadan began on July 19.

Nasser Ishtayeh/AP
A Palestinian woman buys traditional Ramadan decorations at a market in the West Bank city of Nablus, ahead of Ramadan, Tuesday, July 9, 2013.