The Solemnity of the Immaculate Conception is observed as a Holy Day of Obligation throughout the Ordinariate of the Chair of St Peter. Because it is the Patronal Feast day of the USA, the precept to attend Mass applies even in years where 8 December falls on a Monday or Saturday (general decree of the USCCB, December 13, 1991, and CIC 1246), as well as in years when the Solemnity is transferred to Monday, December 9th (Letter of the Dicastery for Legislative Texts, 4 September 2024).