Not messing with the Zohan
Just my two cents..
I agree with the previous poster... if there are already wall switches that control these transformers, simple fix is to have installed in wall switch timers. These are usually digital and will also allow your client the added benefit of overriding as desired. For example, if they have a party and it runs later than the timer is set, they simply press the switch on the timer and turn the lights back on.
One thing to make sure of is that the timer you get is rated for inductive load.