or The feast of the Annunciation, obviously because Christmas is nine months away exactly (although a normal term pregnancy is in fact 9 months and a bit).  What with the precession of the earth, this used to be the date of the vernal equinox, and became one of the quarter days.  So a good day for paying debts, and such like.

Prayers: the Angelus, the mystery of the rosary, the Hail Mary
Music: anything with bells, or based on or about the angelus or the hail mary
Flowers: yes, lilies? blue, white or gold flowers.