I was thrilled when I first got this watch. Then I started to notice that while it accurately recorded some of my sleep periods it wasn't recording others. So I searched through their facts and buried in there was that the sleep is only recorded from 10pm to 8am. This might be fine for most people but not for those of us that have unusual sleep periods. WHY it doesn't record sleep periods 24 hours a day is really a big question. ESPECIALLY when this fact wasn't in the description. Sleep recording is a main reason I use a smart watch and so far everyone I've used has fallen down in this aspect. The one before this only recorded sleep after you had been asleep for at least 3 hours, but it was 24 hours. NEITHER of these scenarios are useful for those of us that sleep in smaller amounts throughout the day, which is common for elderly people like me. It is really sad that this particular deficit makes this watch unacceptable, since I liked it a lot otherwise.