Only Chinese origin roms contain this feature. So far, no custom ROM maker has been able to implement this feature in their roms. The reasons given are strange.
Some say the Chinese own the patent for this feature
Some developers say the device doesn't actually switch off. Screen and modules are turned off but motherboard is still powered and this enables it to power on yhe phone as per schedule. Old blackberry phones had truly implemented this feature as they had a small button cell inside it and they were able to switch on and off completely because of this cell.
I had an old meizu phone with this feature and it was very useful.
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Yureka plus | Aospextended 20180112 | 2.6gb /system partition | Lawnchair launcher