Al-Hilal: The first visible moon on Earth
A global Islamic calendar can be published by precalculating the presence of the Al-Hilal (the first visible crescent moon on earth).
The Blessings of the Lunar Calendar
From a historical angle, all of the events and celebrations of Islamic history are recorded in the Hijra Calendar
Islamic Calendar: Identity of the Ummah
The Muslim calendar, based purely on lunar cycles, was first introduced by the second Caliph, `Umar ibn Al-Khattab using the event of Hijra