Ascension Thurday Tomorrow. Mass Obligation? It depends.

Are you obligated, under penalty of sin, to attend Mass tomorrow because of Ascension Thursday?

"Only the ecclesiastical provinces of Boston, Hartford, New York, Newark, Philadelphia, and Omaha (the state of Nebraska) continue to celebrate the Ascension of Our Lord on Thursday. The faithful in those provinces (an ecclesiastical province is basically one large archdiocese and the dioceses that are historically associated with it) are required, under the Precepts of the Church, to attend Mass on Ascension Thursday" source:  http://catholicism.about.com/od/holydaysandholidays/f/Ascension_Holy.htm