Eid al-Adha - "Feast of the Sacrifice" or the Feast of the Sacrifice is the second and largest of the two major holidays celebrated in Islam (the other being the Eid al-Fitr). It honors Abraham's willingness to sacrifice his son Ismail in obedience to God's command.
However, before Abraham could sacrifice his son in the name of God, and because of his willingness to do so, God gave him a lamb to sacrifice in his son's place. To commemorate this intervention, animals are offered as ritual sacrifices. Some of their meat is consumed by the family that offered the animal, while the rest of the meat is distributed to the poor and needy. Sweets and gifts are given, and members of the extended family usually visit and greet them. This day is also sometimes called the Great Eid al-Adha.
However, the celebration of Eid is not mentioned in the Qur'an. In the Islamic lunar calendar, Eid al-Adha falls on the tenth day of Dhu al-Hijjah and lasts for four days. In the international (Gregorian) calendar, dates change from year to year, moving about 11 days earlier each year.
Iran National and Public Holidays