Me too. We are getting lost in technical details. And with time, you get timing/concurrency problems, so you have to program failsafe.
For me, using a variable time to switch on the light, the principle is as follows, something like a task scheduler:
1. Every day at 13:00 calculate the time to switch on the light, store it in variable SwitchOnTime
2. Every 5 minutes, check if ActualTime > SwitchOnTime
3. If so switch on lamp
4. Disable 5 minute task
That seems quite easy😁
Using this as a starting point, optimizations are possible, and technical choices shall be made during implementation. For example, in a task scheduler you just delete an executed task from the task list. Here you might use a variable to indicate of the task (switching on the light at a variable time) has been executed.
Edit: Cronjob is task scheduler: see [APP][Pro] CronJob - Trigger Flows with Cron Expressions
