Eid-ul-Adha or 'Celebration of Sacrifice' is also known as the Greater Eid. It is the second most important festival in the Muslim calendar and marks the end of the Hajj, the annual pilgrimage to Makkah (Mecca). It takes place on the 10th day of Dhul-Hijjah, the last month of the Islamic calendar..Why do we celebrate Eid-ul-Adha?