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.

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

The ramifications of missing a due date can range from simply adjusting the date to getting fired. Don't take chances with deadlines when a simple conditional format can remind you.