Eid marks the end of Ramzan, when Muslims across the world fast from dawn to dusk. Just as the month of Ramzan began with sighting of the crescent moon, Eid festivities will also begin only after the moon is sighted. So, countries where the moon was seen yesterday celebrated Eid on Wednesday (July 6).
In India, barring Kerala and Jammu and Kashmir, is being celebrated today (July 7). Saudi Arabia and other Gulf countries offered Eid prayers yesterday.
Every year, the dates for Ramzan and Eid change. This is because Muslims across world follow the lunar calendar and there is a difference between the lunar and Georgian calendar.
The lunar calendar is based on phases of the moon and is shorter by 11 or 12 days from that of the Georgian calendar. Therefore, in 12 months of the lunar or Islamic calendar, there will be 354 or 355 days. Every year, the dates move backwards if you compare the lunar months with the Georgian calendar.
Therefore, Eid celebrations vary from country to country and region to region depending of their geographical location.
According to Islamic traditions, the Muslim calendar began when Prophet Mohammad migrated from Mecca to Medina. This migration is called Hijr which took place in 622 AD.