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

You can change the date format in Google Sheets and customize the appearance of calendar dates in a spreadsheet.

It's easy to change the date format in Microsoft Excel. You just need to use the "Date" drop-down menu, which gives you plenty of options.

The default active cell format in Microsoft Excel isn't all that easy to see, but you can use this easy-to-implement code solution to change that.