Holy Day of Obligation - Saturday, December 8th -- Immaculate Conception of the Blessed Virgin Mary

Mass Times
Friday, 5:30pm - Vigil Mass for Immaculate Conception
Saturday, 9am - Solemn Mass for Immaculate Conception (with incense)
Saturday, 5:30pm - Vigil Mass for Sunday

Any Mass from Friday evening through Saturday evening will fulfill the obligation (including the Saturday evening anticipatory Sunday Mass) - most agree that the Saturday evening Mass can't "count" for both the Holy Day and Sunday, in other words, you have to attend Mass twice, once for Immaculate Conception and once for Sunday.

For those in the USA who are wondering -- YES, December 8 is an Holy Day of Obligation, even tho it falls on a Saturday. For other Holy Days, if they fall on Saturday or Monday, the US Bishops have lifted the obligation - but because the Immaculate Conception is the patronal feast of the USA, the obligation is retained even when December 8 is a Saturday or Monday (likewise with Christmas).