For editing a reservation request (before a recipe is reserved) we have a nice little thingy which allows me to enter a duration in either seconds, hours, or minutes. Once the recipe is reserved, there is a separate view for extending the reservation (click "Extend the reservation" on the reservation tab of the recipe page). Currently it only accepts seconds. It should use the same widget, so that I can enter a number of hours instead.
As it so happens, I've got a fix right here in my pocket:
This bug fix is included in beaker-server-24.0-0.git.204.bf63e0d which is currently available for download here:
Beaker 24.0 has been released.