You can edit your current or past periods at anytime by clicking the Period button on the upper righthand corner of your home page (or, if you're using Android the calendar icon) or by clicking your first Daily Gem and then clicking "Calendar View" at the center of your cycle visual. Simply tap on any day to add a new cycle. To edit a period, tap on it and then drag the blue circles around until the start and end dates are correct and click “Save” on the upper right corner. To delete a period, tap on it and then click the “Delete” button on the top of the screen. Please note that the lighter cycles in the future are your period predictions and cannot be edited. But they will automatically update if your period starts earlier or later than expected.