Dates in Excel are serial numbers that start on 1/1/1900, which is represented by the number 1. In the example shown, the formula in cell D6 simply subtracts the numeric value of 1/1/1999 (36161) from the numeric value of 1/1/2000 (36526) to get a result of 365. The steps look like this:
=C6-B6 =36161-36526 =365
Working with today
To count the number of days between an earlier date and today, you can use the TODAY function:
To calculate the number of days between a later date and today, use:
Note that TODAY will recalculate on an ongoing basis. If you open the workbook at a later date, the value used for TODAY will update and you will see a new result.
The DAYS function
The DAYS function calculates the number of days between two dates using a start date and an end date. With a start date in A1 and end date in A2:
Will return the same result as:
Both dates must be valid Excel dates or text values that can be coerced to dates. If start and end dates are reversed, DAYS will return a negative number.