1 Jan 2011 (Friday): The Solemnity, Mary, Mother of God. This is a holy day of obligation when it falls on a Tuesday, Wednesday, Thursday, Friday or Sunday.
9 Mar 2011:
Ash Wednesday. This is not a holy day of obligation but marks the beginning of Lent.
5 Jun 2011 (Sunday): Ascension of the Lord. This is celebrated on the 40th day after Easter commemorating the Ascension of Christ into heaven.
15 Aug 2011 (Monday): The Assumption of the Blessed Virgin Mary, a Solemnity. This year the precept to attend Mass is abrogated. This day is a Holyday of Obligation when it falls on a Tuesday, Wednesday, Thursday, Friday, or Sunday.
1 Nov 2011 (Tuesday): All Saints, a Solemnity. This day is a holy day of obligation when it falls on a Tuesday, Wednesday, Thursday, Friday or Sunday.
8 Dec 2011 (Thursday): Immaculate Conception of the Blessed Virgin Mary, is always a Holyday of Obligation except when it falls on a Sunday in which case it is celebrated as a Solemnity on the following Monday, but not as a Day of Obligation.
25 Dec 2011 (Saturday): Nativity of the Lord, The Solemnity of Christmas has always been a Holyday of Obligation, regardless on what day of the week it occurs.
Find additional information on the Liturgical Year on the website of the United States Conference of Catholic Bishops
Military Archdiocese Website