Why is Eid performed on different days by different Mosques?

Answer 1

The Islamic calendar is based on lunar, rather than solar, months; each month begins when the moon is sighted. Some Muslim communties are located in desert areas where the phases of the moon may be observed on almost every day of the year (there are few clouds), whereas others are located in areas where there are few days when the sky is clear. Some coummunities prefer to follow the moon sightings announced in Saudi Arabia, the birthplace of Islam, where the sky is cloudy fewer than 50 days per year. Others prefer to go by local moon sightings. There is a provision in Islamic law that if the sky is cloudy two days in a row, the new moon may be presumed to have appeared on the third day when it was expected. For this reason, there may be as many as three days' difference in the dates when Muslim communties in different locations may celebrate Islamic feasts.