After a month of testing, I've come to the conclusion that this watch is absolutely not up to scratch for sleep. The big problem is that it doesn't detect the time you fall asleep very well.
This night again, it tells me that I fell asleep at 1:45 a.m. even though I slept straight from 10:50 p.m. Is this the sleep recording by the Firstbeat Analytics system that is the cause ?
I'm bringing out my little Venu Sq which is much better and reliable for sleeping. Let me know when the Vivoactive is ready for sleeping.