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 ...

Press "Ctrl-V" on your keyboard to paste your copied date into the selected cell. Excel automatically formats the date to the default date format set for the current spreadsheet.