For example, is there a command that allows you to turn on the computer (be it a remote computer connected to the network or your own), for example, after a reboot, after a specified, strictly defined, period of time?
Is there a reverse command shutdown -s -t, for example (after turning off the computer), setting delayed switching-on after a specified period of time? Would it be possible to make it automatically turn on by a certain period of time, something like a delayed reboot with some time gap.
The only possible solution is the one, described by Jeff Zeitlin: Wake on LAN. In BIOS, there are Power related options. Inside them, you can set something like "Wake Up By Schedule". You can tune it to Everyday, at 8:00 AM, for example. But in that case, BIOS is in charge of executing that tuned command "wake_up_the_machine_ every_day_at_8:00AM". That's why WoL is developed - to override such limitations. If you use a computer with UEFI BIOS, you can program the UEFI by your code so the computer wakes up at the desired time.