Hi,
sleep tracking is automatic. As far as I know, there is no way to switch the band to "sleep/night" mode manually. But automatic detection works fine for me. Please note that time you spent in bed is not equal to time you really slept. 🙂 From my point of view, automatic tracking is the best way.
Anyway, there is no "sleep time" indicator on the band's activity details screen even if the picture shows it. I don't know the reason. But it is visible in Lifelog application and official release notes for SmartBand Talk application claims that sleep monitoring and smart alarm features were added, sleep monitoring data are available in LifeLog application and future improvements will come. So, I think that current state is intended behavior for some reason and Sony will change it in the future. Of course, smart alarm works for me and the band wakes me up within the defined time period according to sleeping time statistics. 🙂
