There's nothing in Aruba that I know of that will power down a RAP at specific times, but you can disallow clients from connecting to its VAPs during specific times. I'm thinking that's not what you're looking for, but that's as far as Aruba can go.
The only other thing I can think of is if the AP is connected to a switch that is providiing PoE, you could write a scipt that logs into the switch, does a shutdown on the AP's port, then does a no shut when you want it back up.