Do not disturb mode for a few hours

I want to be able to turn on "do not disturb" mode for a few hours (while I'm in a concert, etc). I know that I can manually turn it on, but then I'll forget to turn it off at the end of the concert. (Likewise for turning off the phone.) I could schedule the mode, but then the next day I'll accidentally be in do-not-disturb mode (because I forgot to cancel the schedule). I just want something that says, "Do not disturb for 3 hours". Or maybe "Do not disturb until I leave the current location". Is anything like this available? (Even in an app...)