SleepyTime

Nothing is more important than getting a good night’s sleep, and waking up in a good shape let you make the most of your day! SleepyTime is an app designed to help you wake up in-between sleep cycles and allows you to start the day with a clear mind.
Every time you sleep, you enter into a series of sleep cycles that last for around 90 minutes, but even if you seem to get plenty of hours of sleep, waking up during one of the cycles can make you feel groggy and exhausted. SleepyTime for Android allows you to try and work around this issue.
The app supports calculating when to wake up, when to go to sleep, and when to wake up if you sleep now. You can then set up an alarm to wake up at the right time. The app is perfect for those with a tight schedule, students, and pretty much anyone who wants to stay in top shape! Skeptical? Try it!
Read more about how it works here:
bits.blogs.nytimes.com/2013/02/27/test-run-sleepytime-a-bedtime-calculator
Read more about sleep here:
helpguide.org/life/sleeping.htm
Link to Plus version with widgets and no ads:

===Reviews===
When Should You Be Waking Up?
http://thenerdyrobot.com/when-should-you-be-waking-up/
===What this app does===
-Calculates when to wake up and when to sleep to feel great
-Calculate when to wake up if you sleep now
-Get a list of possible times
-Add an alarm by clicking on a time
-Option to take into account the time it takes for you to fall asleep
-Option to use the 24 hours format or the AM/PM format
-Widgets on homescreen and lockscreen (Jellybean 4.2 +)
>Plus users get an enhanced widget.
-(Plus Only) No Ads
===What this app does not===
-It’s not an alarm app by itself, it only adds it to your android alarm clock app
-Cook for you
-Do your homework
Inspired by sleepyti.me (by David Shaw).
Spanish translation thanks to Carlos Vázquez
Ukrainian/Russian translation thanks to Vlad
Catalan translation by Ariadna
Italian translation by Zokru
German translation by Ilian
Portugese translation by Antonio Pereira
Japanese translations by Yudai Kai
French Translation thanks to Vincent Airiau
Arabic Translation thanks to i7mmodi
Hungarian translation thanks to Bihari Kristóf
Czech translation thanks to Vilem Danzig
Dutch translation thanks to Perry K.
Indonesian translation by Nurahmat Agustianto
Contact me if you wish to translate this app!