Muslims celebrate 'Eid ul Fitr on the first day of Shawwal -- the
tenth month of the Islamic calendar, following the month of Ramadhan
(in which the revelation started and ended 20+ years later, and
which is also the month of fasting). Following a Lunar calendar,
Muslims mark the beginning of the month with the sighting of the new
crescent.
The month long fasting of Ramadaan culminates into the festival of 'Eid-ul-Fitr
(the Festival of Fast-Breaking). It is a festival of joy, family
reunion and thanksgiving to Almighty God. The giving of a special
charity for this occasion is obligatory. This is known as Zakat.
Muslims dress in holiday attire, attend a special community prayer
in the morning, and visit friends and relatives. Greetings of "'Eid
mubarak," or "a blessed 'Eid" are exchanged.