I've been tracking my sleep lately. Garmin says wear the watch two hours before going to bed to get accurate tracking. In my experience this is true. If I put my watch on at 10:00 P.M., and go to sleep at 10:30 P.M., the next morning in will show something like midnight or so for falling asleep. When I have it on for two or more hours before I go to bed it is usually significantly closer to reality. My question is why?
I have 10:30 p.m. as my usually start time, and if I put the watch on an hour early . . . 9:30 P.M., I sync it, walk around a little, move my wrist around and go to bed right at 10:30 P.M. why isn't that enough for the watch to detect I've actually gone to sleep at 10:30 P.M., as I inputted as my usual sleep time. I'm sure I have the same 'lower heart rate" and "lack of movement" as if I had been wearing it for two hours. Why does the sensors or the algorithm need a full two hours to be able to detect a sleep time?
AND....none of probably have a good answer for this, so speculation is encouraged. 
