★The rating 4.9★ period calendar! Popular in 63 Countries. Trusted by 300 million Users. Keep track of your menstrual cycles with Period Calendar. It tracks your periods, blood flow, cycles, ovulation and the chance of conception. Period tracker helps both women looking to conceive and those trying to birth control. Period Tracker is useful, whether you have irregular periods or regular periods. It can track your chance of pregnancy every day. You can also record your menstrual flow, cerv