Commentary: Wayback Machine. In a charming chronological coincidence, due to the timing of Easter in 2016, last year the Solemnity of the Annunciation was observed on this same date, 4 April.
A reflection on the Annunciation: American Catholic Blog. Since life begins at conception (though of course Jesus has existed eternally, long before His conception within the womb of the Blessed Virgin Mary by the overshadowing of the Holy Spirit), by my reckoning the Annunciation ought be regarded as the dividing line 'twixt Before Christ (B.C.) & anno Domini (A.D.), meaning "in the year of the Lord."
Quoth the Holy Redeemer bulletin:
The feast of the Annunciation of the Lord celebrates the angel Gabriel's appearance to the Virgin Mary (Luke, 1:26-38), his announcement that the Blessed Virgin had been chosen to be the Mother of Our Lord, & Mary's fiat—her willing acceptance of God's holy plan.'Twas also the festival of Saint Ælfwold of Sherborne, Bishop (died 1058, A.K.A. Ælfwold II): Saint-link & Wikipedia-link.
Commentary: Wayback Machine.
'Twas also the festival of Saint Margaret Clitherow, Martyr (1556-1586), the "Pearl of York," martyred in the reign of the queen Elizabeth I, one of the Forty Martyrs of England & Wales: Martyr-link & Wikipedia-link; Wikipedia-link XL.
Commentary: St. Margaret was the aunt of the priest & martyr Bl. Robert Middleton, S.J. (3 April).
Scripture of that Day
The Book of Isaiah, chapter seven, verses ten thru fourteen & chapter eight, verse ten;
Psalm Forty, verses seven thru eleven;
The Letter to the Hebrews, chapter ten, verses four thru ten;
The Gospel according to Luke, chapter one, verses twenty-six thru thirty-eight.
Commentary: Lenten Gospel reflection: Word on Fire.