Comment by TeMPOraL

That doesn't explain lack of such functionality at the OS/platform level. It technically exists on Linux and Windows, but is heavily optimized towards sysadmin use, and essentially hidden from regular users on the "normie UI surface". Most people don't even realize their computers could do things on a timer.

(And on Android, AFAIK there's exactly nothing at all. There's not even common support for any kind of basic automation; only recent exception is Samsung. From third-party apps, there's always been Tasker - very powerful, but the UX almost makes you want to learn to write Android apps instead.)