Using specific date and time formats, you can display a date or time in many ways. That’s not how Excel stores a date, though—not as the formatted string that you see.

Create a custom date format based on one of Excel's standard date templates. For example, set all months to display as two digits by adding another "M" to the month format code. Advertisement ...

If you enter 4/5, Excel will interpret the entry as a date and display it as a date, 4/5 or April 5. If you don’t realize it, that “date” will not evaluate as you expect.

You can set Excel to display dates in a variety of ways, no matter how you type in the data. Here's how to find and change date formats in Excel on a Mac or PC.