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

The date will display in the format you choose, no matter how you enter it. If you type "1/1/19" into a cell with the long date format, Excel will change it to the expanded date.

Feed it a cell reference or text string, and Excel will handle the rest. Let’s say you're migrating data from a database where names were entered in all caps and want them in a friendlier format.