We plan to make a day trip to Belfast from Dublin. Ideally from a scheduling perspective, we would do this on Sunday. But as I take a closer look, it sounds as if some places may be closed until the afternoon on that day of the week. So, I'm thinking we should move our Belfast day trip to a Monday. Does that sound like a good idea? Or does it really matter? Thank you!
I think that is something you will need to decide by comparing the Sunday and Monday hours of what actually it is you want to see in Belfast, as well as the availability of whatever it is you would want to do in Dublin on the day you didn't go to Belfast. It's true that some things may have shorter hours on Sunday. But Monday can be a typical day for closure altogether, especially of museums.