For now, I created time ranges with ±15 min time window both on power on and power off via timers (1 timer for power on at time n ± 15 min, 1 timer for power off at time m ± 15 min)so I have a bit of randomization (0-15 min before and after specified time). I will check other solutions if needed.

Thanks a lot Schadwick for give me a tip! … kinda :D.

Woah… that’s so coool!.