How do I fix my period dates?

To edit your period dates:

Select "Calendar" from the bottom bar
Select the day you would like to edit
Tap the "period" data category in the section below the calendar
In the "period" section of the data logging page, enter "nothing" to remove period data or "period" to add period data. You can also add flow details, or change a period to "spotting"
Tap "Save" (iOS)/check mark (Android) in the top right corner to save

Please repeat this for each day that your period is incorrect or so that Ovia can adjust its predictions.