Masses for the feast of the Immaculate Conception are at 7:00 am, 9:30 am, and 7:00 pm.
Here’s a little more information on the feast of the Immaculate Conception:
In teaching that Mary was conceived immaculate, the Catholic Church teaches that from the very moment of her conception, the Blessed Virgin Mary was free from all stain of original sin. This simply means that from the beginning, she was in a state of grace, sharing in God’s own life, and that she was free from the sinful inclinations which have beset human nature after the fall.
The Solemnity of the Immaculate Conception, in its oldest form, goes back to the seventh century, when churches in the East began celebrating the Feast of the Conception of Saint Anne, the mother of Mary. In other words, this feast celebrates, not the conception of Christ (a common misconception), but the conception of the Blessed Virgin Mary in the womb of Saint Anne.