The day of commemorating in honor the Archangel Gabriel is the day of his Synaxis, because Christians gather together on the other day of Annunciation to glorify the heavenly messenger of the great mystery of the incarnation of the Son of God. St. Gabriel is one of the seven spirits, "who present the prayers of the saints and enter into the presence of the glory of the Holy One" (Tobit 12:15) [Dan.9:21].
The name Gabriel means "might of God". Gabriel in the service of the salvation of mankind is especially revealed as the herald and minister of the omnipotence of God. So, wasn't he revealed as the might of God in the wonderful conception of the Forerunner from aged parents? Gabriel announced this conception. Wasn't he the one to predict the seedless conception of the Very Son of God? - Gabriel had the honor of the annunciation about this. Wasn't this the same Archangel, according to the opinion of divinely wise men, sent to support the Savior in the Garden of Gethsemane and to announce to the Mother of God Her all-honorable dormition?