Feast Day Of Saint Gabriel The Archangel - 24 March

Quoted from Wikipedia [1]:

Saint Gabriel the Archangel's festival day was exclusively celebrated on 18 March according to many sources dating between 1588 and 1921...

The feast of Saint Gabriel [the Archangel] was included by Pope Benedict XV in the General Roman Calendar in 1921, for celebration on 24 March. In 1969 the day was officially transferred to 29 September for celebration in conjunction with the feast of the archangels St. Michael and St. Raphael.

Quoted in part from Catholic Exchange [2]:

1. Messenger

The word Angel, from Greek, means Messenger. Gabriel is sent from the throne of the Triune God, Father, Son, and Holy Spirit, as a Messenger. These Divine and Angelic messages are of the greatest importance. First, that John the Baptist will be born despite the advanced age of his Mother, St. Elizabeth. Second, the greatest message of all times will be delivered on the part of the Archangel Gabriel and that will be to Mary.

2. The Annunciation

The Archangel Gabriel announces to the Blessed Virgin Mary the greatest message in the history of the world—namely, that Mary is chosen by God to be the Mother of Jesus, the Savior of the world. Never was there a more important message...in the history of humanity, that Jesus, the Savior will enter the world through the announcement of the Archangel Gabriel and the consent of the humble Virgin of Nazareth.

3. The Hail Mary

The prayer that is recited millions of times every day throughout the entire world, has as its origin the words and the announcement of the Archangel Gabriel—“Hail Mary, full of grace….” For that reason, the technical name of the Hail Mary is really “The Angelic Salutation”—the greeting of the Archangel Gabriel. This being said, every time we pray the prayer that Our Lady loves most, we start off the prayer using the words of the Archangel Gabriel. How important is this angel and how underestimated he is in the history of salvation!

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5. Mary’s Consent Witnessed by the Archangel Gabriel

The conclusion of the dialogue between the Archangel Gabriel and the Blessed Virgin Mary culminates in Mary’s consent, in Latin, Mary’s FIAT: “Behold, I am the handmaid of the Lord; let it be done to me according to your word.” (Lk. 1:38) Not only does the Archangel Gabriel deliver this all-important message to Mary, but he hears and witnesses what can be considered among the most important words in the history of the world’s salvation....

[1] https://en.wikipedia.org/wiki/Gabriel, quoted without hyperlinks and references.

[2] https://catholicexchange.com/archangel-gabriel-the-power-of-god