My 965 does for me. It pretty much nails by “Bed Time” and “Wake Time” to the minute.
Granted I’m like C3PO. I’m unconscious before the head hits the pillow and sproing up as soon as the first hint of pre-dawn natural light comes through the window.I live in a house with 2 dogs and a lot going on. Sometimes when a dog barks early, I might lie still but not sleeping for the last 1/2 hour more more of the night. Or I will wake in the middle of the night for a bit when a massive storm is raging. The Garmin will almost always call that REM, whereas the Fitbit is almost 100% accurate in assigning that to awake time. The Garmin is pretty good at getting sleep and wake times, it is just the awake time in the middle that it sucks at - and it inflates its REM time because of that.