I’m sure this question will be coming, so I thought I’d try to get out in front of it for those who may think of it at the last moment and start to panic.
Here are the guidelines for this year from the USCCB (page 7):
- Since December 8, 2013, is the Second Sunday of Advent, the Solemnity of the Immaculate Conception of the Blessed Virgin Mary is transferred to Monday, December 9, 2013. The obligation to attend Mass, however, does not transfer. The Optional Memorial of Saint Juan Diego Cuauhtlatoatzin, December 9, is omitted this year.
So there is no obligation to attend Mass on December 9, 2013 to celebrate this solemnity. There is, of course, the obligation to attend Mass on December 8th, as it is a Sunday.
Note that this is for this year only and for the United States only. Other locales will have to check with their local bishops’ conference to see what has been decided for them (maybe it’s the same, maybe not).
But going to Mass is never a bad thing. So feel free to go anyway.