According to Islamic calender, Eid Al-Adha occurs on the 10th of Lunar month of Hijjah. Unlike the discrepancies in sighting of moon, which tells us about the end of the month of Ramadan and the beginning of Shawwal, sighting of new moon for Hijjah was determined some 10 days before.
Because of the fact that millions of people who perform Hajj to Mecca must perform this ritual in some specific days. It would be nonsensical for any person to perform Eid Al-Azha on any other specific day, because Eid must follow Day of Arafat and it lies is the 9th Day of Dhul Hijjah.
Muslims who are not pilgrims celebrate the Eid on the day following the day of Arafat, with some congressional Eid prayers which is then followed by a special khutba like that of Eid-ul-Fitr. It is not obligatory to stay for Khutba of Eid. Once 2 rakat of Eid prayers have completed, many people go out to make sacrifice. If you Learn Quran, you can better understand the importance of Eid Al-Adha.
After the prayer, people sacrifice animals or proper livestock that they can afford. One third of the animal goes to family, one third to poor, and one third to friends and relatives. However, it is recommended to give as much in charity as possible.