You can change the date & time format in Google Sheets & Excel Online using this guide. Use different date & time formats in spreadsheets.

When you enter a date that's formatted with slashes, Excel will recognize it as a date. For example, Excel will automatically choose the date format for a cell that contains 11/11/19. You can set ...

How do I change a number into a date format in Excel? Microsoft Excel has a feature that allows you to convert a number into a date, which is quite simple to do.