Holy Days of Obligation are certain days of the year on which all Catholics are required to attend Mass. If the Holy Day falls on a Saturday or Monday, the obligation to attend Mass on that day is removed, and the Holy Day is celebrated on that Sunday.
Every Sunday is a Holy Day of Obligation in the sense that Catholics are required to attend Mass every Sunday.
Sunday, January 1: Solemnity of Mary, the Holy Mother of God
Sunday, May 21: The Ascension of the Lord (Permanently transferred tot he 7th Sunday of Easter in Florida)
Tuesday, August 15: Assumption of the Blessed Virgin Mary
Wednesday, November 1: All Saints Day
Friday, December 8: Solemnity of the Immaculate Conception
Monday, December 25: Solemnity of the Nativity of the Lord (Christmas)