Q: When can the Udhiyyah animal be slaughtered?
A: The time for slaughter begins after the earliest Eid prayer, excluding the sermon, in the region is complete. This time can be estimated by those who do not attend the prayer due to their residence being in a location where Eid prayer is not performed. People who live in a region in which Eid prayer is performed are not permitted to slaughter the animal before the prayer concludes. If they do, it will not count for them and they will need to slaughter another animal. If Eid prayer is missed, the slaughter can be performed after the zawāl. The time of slaughter extends to the end of the second day of tashrīq i.e. the 12th of Dhul Hijjah. According to Imam Ahmad, there are three days for slaughtering. It is best to slaughter the animal on the first day which is Eid day and then the day after. It is permitted to slaughter the animals during the nights as well. If that time expires, an obligatory Udhiyyah must be made up in the same way and a voluntary Udhiyyah is voided. Source: Sharh al-Muntaha
This answer was collected from HanbaliDisciples.com. The questions have been answered by Imam John Starling.