...girls who travel back in time....? One of them has an aunt that lives in an old house. In the attic there is a trunk full of costumes. When they put on the costumes and stand in front of the mirror (maybe the spin it) they go back in time. They usually did it one at a time. Once they were there there would be some sort of problem they would have to solve.
One girl put on a Victorian dress and went back in time to where she was a daughter of a rich family.
Another one, one of the girls put on a Persian outfit and went back in time to where she was a princess in Persia.

I have been trying to find these books for so long.