When you first download the Ava Fertility app, it will ask you a series of questions, including when your last period was. 


Knowing when your last period was helps establish some background about your cycle history and helps the algorithm know which cycle day you are currently on, in order to display the information appropriately. 


If you don’t remember when your last period was, you can simply select “I don’t know”, and when your next period comes, you can enter those dates into the app by selecting the + icon.