Period-tracking apps can be very useful for helping you tune into what's going on with your menstrual cycle. Over time, they offer you an opportunity to identify your "normal" when it comes to your period. Most apps let you track the dates of your period as well as your symptoms, giving you a chance to recognize patterns and plan accordingly. For example, if you know that you often feel nauseated and exhausted around the same time every month, you may not want to schedule anything too taxing at that time.