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.

Excel has a surprising limitation that you may not discover until you try to enter more than 15 digits in a cell. The application can only store numbers with15 digits of precision.

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 ...