A free program for Android, by Robert Londo.

What is Period Tracker, and how does it Work?

This free period and ovulation tracker app lets you track your menstrual cycle and identify the days you are most fertile. With it, you can also get reminders and graphs to track your fertility. You can use it for birth control, preventing pregnancy, and regular cycle tracking. It is a free, simple, and beautiful menstrual cycle calendar.

How do I use it?

You can log the start and end dates of each period in the calendar.

If you are interested in pregnancy, you can also track when you are most fertile, and get a daily reminder of the fertile days.

You can use it for regular cycle tracking, and it can help you predict the day of your next period.