Excel may return a serial number instead of a date; because it is stored thus in the backend. Learn how to convert Serial Number to Date.

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.

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