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

How to Auto-Format the Date in MS Excel. When you create Microsoft Excel spreadsheets that contain one or more columns of dates, you can make things a bit easier if you pre-format your cells to ...

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.