Any app that can track when I go to sleep and when I wake up?

I have tried a few but they all seem to be putting the priority on features I don't need, like recording the sounds while I sleep. I would just like a log of when I fall asleep and when I wake up.

EDIT: Here is my plan B, until I find an app: when I go to bed, I send a text message to myself. When I wake up, I do the same. It gets automatically time-stamped. Example:

"Ok Google, send a text saying Good Night to NemoWuming"

"Ok Google, send a text saying Good Morning to NemoWuming"