https://www.archgh.org/resources/holy-days-of-obligation/

Assumption - Assumption of Mary Into Heaven 

[ 1]  At their November 1991 meeting, the National Conference of Catholic Bishops decided that whenever January 1, the Solemnity of Mary Mother of God or August 15, the feast of the Assumption of the Blessed Virgin or November 1, the Feast of All Saints falls on a Saturday or a Monday, the precept to celebrate Mass is dispensed. The Congregation for Bishops confirmed the action on July 4, 1992.

Although the obligation to celebrate Mass when these three holy days fall on a Saturday or Monday is abolished, parishes are to continue to observe these holy days by scheduling one or more Masses at a convenient time so that people who wish to participate are able to do so.