Which calendar???

I have a dilemma. I just read here about the Nativity fast starting on the 15th (yes I know I should have better methods than happening upon it in other's blogs to keep track of the fast and feast days! I have yet to get into the habit of checking my church calendar regularly :S). Now the two parishes I attend most of the time here in Montreal are both new calendar, but the church my mom attends, and the one I will be attending as well for Christmas when I visit my family (they live an hour north in Rawdon) is old calendar.

Hmmm, actually Jan. 7 falls on a Wednesday, and depending on what vacation days I get I might not even be able to visit my parents then. But I'll be with my family on Dec. 25th for sure, and there's no new calendar church in my parents town that I know of, and anyways I would have liked to go to church with my mom. So how do I get to church for Christmas?!? If I follow the new calendar, I'll be at my parents on Dec. 25th, and there's no new calendar church there. If I follow the old calendar, I'll be all out of whack with the services I'll be attending here in Montreal, and not even sure if I'll be able to make it to my parents on Jan 7th. Last year I had Jan 7th off, so I went to church with my mom (I think? I don't remember...). Argh. I have to talk to my priest. My mom thinks that her parish will eventually switch to new calendar sometime, which will be nice if I can avoid this confusion again.