Eid al-Fitr begins at sunset after the first sighting of what?

Eid al-Fitr begins at sunset after the first sighting of the crescent moon.

This timing follows the Islamic lunar calendar, whose months begin with the appearance of a new crescent. Eid al-Fitr marks the start of Shawwal, the month after Ramadan, so the sighting ends the Ramadan fast and announces the festival.

Visibility can differ by location because the crescent may be hidden by clouds, atmospheric conditions, or daylight. Muslim communities therefore sometimes celebrate Eid on different Gregorian dates, depending on whether they use local testimony, astronomical calculations, or an accepted sighting elsewhere.

A common mix-up is confusing the crescent that begins Shawwal with the full moon in the middle of a lunar month. The crescent is also why Eid dates move earlier by roughly 10 or 11 days each Gregorian year: the Islamic lunar year is shorter than the solar year.