When:
December 8, 2017 all-day
2017-12-08T00:00:00-07:00
2017-12-09T00:00:00-07:00

On December 13, 1991 the members of the National Conference of Catholic Bishops of the United States of America made the following general decree concerning holy days of obligation for Latin Rite Catholics:

In addition to Sunday, the days to be observed as holy days of obligation in the Latin Rite dioceses of the United States of America, in conformity with canon 1246, are as follows:

January 1, the solemnity of Mary, Mother of God
Thursday of the Sixth Week of Easter, the solemnity of the Ascension
August 15, the solemnity of the Assumption of the Blessed Virgin Mary
November 1, the solemnity of All Saints
December 8, the solemnity of the Immaculate Conception
December 25, the solemnity of the Nativity of Our Lord Jesus Christ

Whenever January 1, the solemnity of Mary, Mother of God, or August 15, the solemnity of the Assumption, or November 1, the solemnity of All Saints, falls on a Saturday or on a Monday, the precept to attend Mass is abrogated.

This decree of the Conference of Bishops was approved and confirmed by the Apostolic See by a decree of the Congregation for Bishops (Prot. N. 296/84), signed by Bernardin Cardinal Gantin, Prefect of the Congregation, and dated July 4, 1992.

http://www.usccb.org/beliefs-and-teachings/what-we-believe/canon-law/complementary-norms/canon-1246.cfm

http://www.usccb.org/about/divine-worship/liturgical-calendar/upload/2018cal.pdf