The list of Days of Obligation includes all Sundays. Some feasts, like Easter, are always celebrated on Sundays, so they are always obligatory.

Wed, January 1 - Solemnity of Mary, Mother of God

Wed, March 5 - Ash Wednesday

Sun, June 1 - Solemnity of the Ascension of the Lord

Fri, August 15 - Solemnity of the Assumption of the Blessed Virgin Mary

Mon, December 8 - Solemnity of the Immaculate Conception of the Blessed Virgin Mary

Thu, December 25 - Solemnity of the Nativity of Our Lord Jesus Christ