I land in Paris on the morning of Sunday 11-May which is Pentecost/Whit Sunday and will be there for the week.

I had assumed that most things would be closed on the Sunday, but didn't realise that they'd also all be closed on the Monday. Is there somewhere to figure what is opened/closed? I'm currently under the impression that stores/banks and many restaurants will be closed but tourist sites (ones that aren't closed all Mondays) will be open. What about department stores like Printemps?

Any advice would be great.
Thanks.