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

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.

If the Excel Date Filter is not grouping by month, enable grouping dates in the AutoFilter menu, set dates in the proper format, etc.

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.