You can add a zero before a number in Google Sheets and Excel using this tutorial. You need to change cell formatting or use function.

When you type a seven-or-ten-digit phone number into an Excel cell that uses the phone number format, Excel will automatically change the way the number looks so that it appears as a phone number.

Excel considers dates and times as numbers in cells, making calculation difficult. Excel processes 6 AM as "0.25," because it is one quarter of the way through the day. If you need to add a number ...