December 8th, Saturday, is the Solemnity of the Immaculate Conception and is a Holy Day of Obligation.
St. Luke Holy Day of Obligation Mass Schedule
December 7, Friday Vigil Mass at 6:00PM
December 8, Saturday Mass at 8:30AM only
It has been clarified by the USCCB (US Conference of Catholic Bishops) that "when consecutive obligations occur on Saturday-Sunday or Sunday-Monday, the faithful must attend Mass twice to fulfill two separate obligations." Therefore, the people are to attend one Mass for the Immaculate Conception (from Friday evening up to 4:00 pm on Saturday the 8th), and a Mass for the celebration of the Second Sunday of Advent (from 4:00 pm on the 8th through Sunday the 9th).
On this most solemn feast, let us worship our Lord by gathering at His Eucharistic table, giving honor to our Blessed Mother as we meditate on the supernatural grace bestowed by God upon her, that from the first moment of her conception, Mary--by the singular grace of God and by virtue of the merits of Jesus Christ--was preserved immune from original sin. She becomes the pristine vessel of the unblemished Lamb of God, Jesus Christ, the only begotten Son of the Father, the Savior of all. O Mary, conceived without sin, pray for us sinners who have recourse to thee.
"Hail, Mary, full of grace, the Lord is with you; blessed are you among women, and blessed is the fruit of your womb, Jesus." (Luke 1:28, 42)