this android application will calculate the safe period that you can have sex in it without worrying about pregnancy, all you have to do is enter the day of the first day of your Menstrual cycle, and a calendar will shown, the green days are safe , the red are not!
http://coding-labs.com/app-safe-period-to-have-sex-without-get-pregnant/
by http://coding-labs.com
minor bugs fixed :)