The hormonal shifts that occur when you get your period can vary depending on your age, physiology, and even just month-to-month based on other environmental, personal, emotional, and work factors.

It's very important to always enter the first day of your period and subsequent days of your period for that cycle. This gives the algorithm a baseline to understand your cycle length and patterns for follicular phase and luteal phases to improve its accuracy in predicting your fertile window and ovulation.