Confused again!!

Sherry • My husband and I are 40, we are going to try and conceive our first child together. I am having my tubes untied next mon
This app changed my ovulation time again this month. When this Saturday was suppose to be my peak time it's saying last Sunday was. It just changed some time today and I have done nothing different. Maybe I should try another app to help me. Any suggestions on the reasons or another app?