Advance Sleep Monitoring

Hi Everyone. 
Got a question.....

With the Advance Sleep Monitoring. 
Am a pilot and i am all over the world. I find it difficult to set manually the sleep time in each country i am in. 
I thought the Garmin Fenix 6 S would recognize on its own when i fall asleep, record the time, in the current time zone am in, and monitor my sleep until i wake up. (A little bit like the fitbit use to do)

Any help on how do i need to do to leave the watch guessing when i fall asleep with the indication of my heart rate instead of the sleep time?

thank you.