For iOS system, you can go to the "Charts" page and click the three dots on the upper right corner then tap the “Share” button, then choose to export BBT data by "Email".

For Android system, follow the same step to click "Email", the app will ask you to input dates for the "Export Period Chart".

Note: Your BBT data would be exported to a file ending with ".csv" that you can send to yourself or other desired email addresses.