How does the Mi Clock app know when I went to sleep?

[jwa11]

What mechanisms does it use to detect this?

 

[Hitardo]

I would assume, a mix of:
- The phone is charging;
- The phone is not moving (accelerometer);
- There is no sound around (microphone).

But I am assuming, based on some things I read online.
This was not exclusive to MIUI, and not limited to phones.