Solemnity of the Immaculate Conception

From diocesan Pastoral Briefings for Oct. 25, 2024:

This is notification that the Solemnity of the Immaculate Conception – observed this year on December 9 – is a Holy Day of Obligation.
In a memorandum received from the Holy See last week, the Dicastery for Legislative Texts responded to the question posed by the USCCB concerning when a holy day of obligation occurs on a Sunday in Advent, Lent, or Easter and the observance is transferred to Monday, does the obligation to participate in Mass also transfer? The Dicastery responded “the feast must be observed as a day of obligation to which it is transferred.”
Therefore, the Solemnity of the Immaculate Conception (Monday, Dec. 9, 2024) is to be observed as a holy day of obligation.