The Feast of the Annunciation is one of the earliest Christian feasts, and was already being celebrated in the fourth century. There is a painting of the Annunciation in the catacomb of Priscilla in Rome dating from the second century. The Council of Toledo in 656 mentions the Feast, and the Council in Trullo in 692 says that the Annunciation was celebrated during Great Lent.
More on the Annunciation at: https://www.oca.org/saints/lives/2022/03/25/100884-the-annunciation-of-our-most-holy-lady-the-theotokos-and-ever-vi