You might be able to use a digital 7 day programmable thermostat where you could set on/off times for the day.
They usually have settings like:
Wake 7am-12pm x degrees
Leave 12pm-3pm x degrees
Return 3pm - 6pm x degrees
Sleep 6pm -7am x degrees
You can change both the times, and temps, and have weekend schedules.
Honeywell makes them.. and you should be able to find one using line voltage.