It is a handy Menstrual Cycle Management Assistant.
There are many apps available in the market,

but I feel it uneasy to operate them.

As a female programmer,
just develop an app for myself.
Menstrual Tracker – Menstrual Cycle Management Assistant APP
Menstrual Period Tracker, the easiest way to track your periods is now on App Store.


Disclaimer: Forecast accuracy depends on a number of factors including how regular one's cycle length is, when one actually ovulates during the cycle, and how many periods have been logged in the app. Anxiety, stress, diet, nutrition, exercise, environment, medications, age and other factors can also affect one's cycle from month to month.