Thursday was the Solemnity of the Ascension of the Lord. But in most of the United States it is celebrated today. Ever wonder who gets to decide if it moves? No, it's not the bishop. It's actually the archbishop, so that an entire ecclesiastical province, composed of an archdiocese and its suffragan (i.e. affiliated/subordinate) dioceses have the same practice. So here in the Diocese of Richmond, we follow the practice chosen by the archbishop of Baltimore. In the ecclesiastical provinces of Boston, Hartford, New York, Philadelphia, Newark, and Omaha, the Ascension is celebrated on Thursday; everywhere else it is moved to the following Sunday.
Curious which ecclesiastical province you're in? Take a look! (Note that this map shows the archdiocese of each province in a slightly different color from the rest of the province. If that confuses, you, try this map instead.)
In the course of digging up the map above, I stumbled upon the historical map below, c. 1912, back when there were only fourteen provinces. You can see that the number of diocese and provinces has proliferated considerably in the past century, to thirty two Latin provinces in the continental US.