Granted. However, while you can set the "undo" time, the time you travel backwards is fixed at two weeks. So if you decide to undo the past hour because you just said something stupid to a relative, you first have to relive the past two weeks motion-for-motion before you get to the "undone" hour and gain control over your actions again.
There's another undo button where the amount of time you travel back is properly synchronized with the amount of time you undo. Unfortunately, it's fixed at an eighth of a second, so you have to press it over and over really fast to go back a meaningful amount. As a result, whenever you do something you regret, undoing it comes at the price of severe finger cramps.
Oh, and that "somewhere" they're stored? It's Area 52, the rightfully obscure sister location to Area 51. You have to ask the people in charge really nicely to take it out of storage. (But first, you have to determine who the people in charge even are and how you'd contact them.)
I wish to know the best possible wish I could make, excluding wishes such as this one that are only to gauge what wish I should make, and for it to be granted alongside this wish.