The Astronomy of Ramadan

Tradition dictates that Ramadan, like other holy months in the Islamic calendar, begins the day after the thin crescent of the new moon is first seen with the naked eye. Because visibility is very dependent on local atmospheric conditions, religious officials in different countries—relying on eye-witness observations from volunteers—often disagree on the exact moment, sometimes by as much as 3 or 4 days. It’s a recipe for international confusion.