The time for offering the sacrifice begins after the Eid prayer on Eid al-Adha and ends when the sun sets on the thirteenth of Dhu’l-Hijjah. So there are four days of sacrifice: the day of Eid al-Adha and the three days after it. 

It is better to hasten to offer the sacrifice after the Eid prayer, as the Messenger (peace and blessings of Allaah be upon him) used to do, then the first thing he would eat on the day of Eid would be meat from his sacrifice. 

Ahmad (22475) narrated that Buraydah (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) did not go out on the day of (Eid) al-Fitr until he had eaten, and he did not eat on the day of (Eid) al-Adha until he came back, then he would eat from his sacrifice. 

Al-Zayla’i narrated in Nasb al-Raayah (2/221) that Ibn al-Qattaan classed it as saheeh. 

Ibn al-Qayyim (may Allaah have mercy on him) said in Zaad al-Ma’aad (2/319): 

‘Ali ibn Abi Taalib (may Allaah have mercy on him) said: “The days of sacrifice are the Day of Sacrifice (yawm al-nahr) and the three days after it.” This is the view of the imam of the people of Basra, al-Hasan; the imam of the people of Makkah, ‘Ata’ ibn Abi Rabaah; the imam of the people of Syria, al-Awzaa’i; and the imam of the fuqaha’ of hadeeth, al-Shaafa’i (may Allaah have mercy on him). It was also the view favoured by Ibn al-Mundhir. The three days are specified because they are the days of Mina, the days of stoning (the Jamaraat) and the day of al-Tashreeq. It is forbidden to fast on these days. It was narrated via two isnaads, one of which supports the other, that the Prophet (peace and blessings of Allaah be upon him) said: “All of Mina is the place of sacrifice, and all the days of al-tashreeq are days of sacrifice.” End quote. 

The hadeeth was classed as saheeh by al-Albaani in al-Silsilah al-Saheehah, 2476 

Shaykh Ibn ‘Uthaymeen said in Ahkaam al-Udhiyah, concerning the time for offering the sacrifice: 

It is from after the Eid prayer on the Day of Sacrifice until the sun sets on the last of the days of al-tashreeq, which is the thirteenth of Dhu’l-Hijjah. So there are four days of sacrifice: the day of Eid after the prayer, and three days after that. Whoever slaughters his sacrifice before the Eid prayer is over, or after the sun sets on the thirteenth, his sacrifice is not valid … but if he has an excuse for delaying it until after the days of al-tashreeq, such as if the animal ran away with no negligence on his part, and he did not find it until after the time was over, or if he delegated someone to do it on his behalf and his deputy forgot until the time was over, then there is nothing wrong with offering the sacrifice after the time has ended, because there is an excuse, by analogy with the fact that one who sleeps and misses a prayer or forgets it should offer the prayer as soon as he wakes up or remembers it. 

It is permissible to offer the sacrifice during that time by night or by day, but it is better during the day, and the day of Eid after the two khutbahs is the best time. Each day is better than the following day, because that is hastening to do good. End quote. 

It says in Fataawa al-Lajnah al-Daa’imah (11/406): 

The days of sacrifice for pilgrims performing qiraan or tamattu’, and for offering the sacrifice (udhiyah) are four: the day of Eid and the three days after that. The time for sacrifice ends when the sun sets on the fourth day, according to the soundest scholarly opinion. End quote.