Web: Mobile-friendly webapp Sleeptime uses your wake up time to calculate when you should go to bed. The goal is for you to wake up at the right part of your sleep cycle so you're well-rested for the morning.
You probably know when you need to wake up, so just scroll the time wheel's hours and minutes to set your wake-up time. Sleeptime will then tell you what time you need to fall asleep at if you want to rest your eyes for six hours, 7.5 hours or nine hours, giving you a full series of sleep cycles so you wake up rejuvenated and refreshed, instead of at the bottom of a cycle. This targets the 90-minute deep sleep cycle, to ensure you wake up refreshed.
Unlike other such web apps we've featured in the past, Sleeptime is mobile-optimised to work on all smartphones. You can also reverse-engineer it to find what time you should wake up at if you're going to sleep right now.