Glow an other apps

Milica
Glow and other apps that help you trac your menstrual cycle will never ve 100% accurate. They predict when your period will star by the information you give them but they don't know your body. Your period can be late or early for many reasons so you shouldn't be worried every time you don't get your period when your app says you will. 
I saw so meni topics about girls bing worried when their piriod didn't start when the app sad it will. 
I hope this helps. ?