What was the hour of the Annunciation? I'm reading Benedict XVI's "Jesus of Nazareth: The Infancy Narratives" and he indicates how Gabriel appeared to Zachariah in the evening. Also Gabriel appears to Daniel (Dn 9, 21) at the same hour:


  As I was yet speaking in prayer, behold the man, Gabriel, whom I had seen in the vision at the beginning, flying swiftly, touched me at the time of the evening sacrifice.


Now, I can't confirm that Gabriel appeared to Zachariah in the evening sacrifice, because there apparently were two "incense sacrifices in a day", one in the morning and another in the evening. But it would make sense if it was in the evening.

Things get more interesting. We only know of Gabriel because of the book of Daniel and because of these two apparitions in Luke. Two of them apparently happened in the evening. What about Mary? Benedict XVI doesn't say as far as I've read but he points out to Psalm 141, 2:


  Let my prayer be directed as incense in thy sight; the lifting up of my hands, as evening sacrifice.


The question therefore is: Do we know of any biblical text that says if Mary was praying before Gabriel's apparition? What about any interpreters, commentaries or traditions that made a case for it?

Thank you all and God bless you.
What was the hour of the Annunciation?

There is nothing in Holy Scriptures that will be of any help here. But perhaps we could start with Dom Guéranger and tradition:  


  A tradition, which has come down from the apostolic ages, tells us that the great mystery of the Incarnation was achieved on the twenty-fifth day of March. [St. Augustine,  De Trinitate.  Lib. iv. cap. v.] It was at the hour of midnight, when the most holy Virgin was alone and absorbed in prayer, that the Archangel Gabriel appeared before her, and asked her, in the name of the blessed Trinity, to consent to become the Mother of God. Let us assist, in spirit, at this wonderful interview between the angel and the Virgin: and, at the same time, let us think of that other interview which took place between Eve and the serpent. A holy bishop and martyr of the second century, Saint Irenaeus, who had received the tradition from the very disciples of the apostles, shows us that Nazareth is the counterpart of Eden. [Adv. haereses. Lib. v. cap. xix.] - MARCH 25 – THE ANNUNCIATION OF THE EVER BLESSED VIRGIN ~ Dom Prosper Gueranger