You can quickly go to your Month view and scroll upwards to change data for previous days.
The very first date with any entered data will be shown on your app, along with 3 previous months in a light grey color. Click on any grey day to add data for that day, and watch the colors change.
You can do this by:
Going to your Month view, tap on the day you wish to add/change data. This will open the Add Data page, where you can add/change any information you want. Then you can either swipe right/left to change the date or press ‘Save.’ As you swipe right or left, the new data automatically save.
If you are an iOS user and have previously been using a fertility or period tracker, you can easily add your past data (temperatures, period, etc.) to the app. To do this, you can go to the menu in the top left corner of your screen > Settings> Integrations > 'Sync with Apple Health.'*
*Please bear in mind that it is not possible to ‘unsync’ the data that you import from Apple Health. For optimal use of the app, we kindly ask you not to sync any recorded data when you were using hormonal birth control, which may negatively impact your predictions. The hormones from hormonal birth control generally work to inhibit ovulation and affect your body temperature, making it impossible to combine with Natural Cycles.