The Prophet (ﷺ) as saying: The two months of 'Id (festival), Ramadan and Dhu al-Hijjah, are not defective.
Sunan Abi Dawud Book 14, Hadith 11
← Previous Hadith We kept fast for twenty-nine days along with the Prophet (ﷺ) more often than we kept fast for thirty days.

Sunan Abi Dawud Book 14, Hadith 10 Next Hadith → The Prophet (ﷺ) said: The end of Ramadan is on the day when you end it, and the 'Id (festival) of sacrifice is on the day when you sacrifice. The whole of Arafah is the place of staying, and the whole of Mina is the place of sacrifice, and all the roads of Mecca are the place of sacrifice, and the whole of Muzdalifah is the place of staying.

Sunan Abi Dawud Book 14, Hadith 12