If you find your Dates keep changing format in Google Sheets, or they are in mm/dd/yyyy instead of dd/mm/yyyy (or vice versa), you may need to update your Locale settings.

1. File -> Spreadsheet settings.
2. Under "Locale," select "Your Country" (this affects formatting details such as functions and dates)
3. Click Save Settings.
4. Next, Highlight the entire Date column (in the logbook page) and re-format it as a Date format.
5. Menu -> Format -> Number -> Date