Because Excel stores dates & times as numbers we can add, subtract and compare dates and times in Excel in the same way that you would add or subtract any other numbers.

The following examples use the date and time values in the example spreadsheet on the right to illustrate the addition and subtraction of dates and times in Excel.

A B C D E
1 Begin End Formula Result Explanation
2 08/20/2014 08/31/2014 =B2-A2 11 Calculates the number of days between 08/20/2014 & 08/31/2014
3 13:00 17:15 =B3-A3 04:15 Calculates the number of hours and minutes between 13:00 and 17:15 – 4 hours and 15 minutes
4 08/30/2014 17:00 08/31/2014 09:00 =B4-A4 16:00 Calculates the number of hours and minutes between 08/30/2014 17:00 and 08/31/2014 09:00 – 16 hours
5 08/30/2014 17:00   =B5+23 08/31/2014 16:00 Calculates the date and time that is 23 hours after 17:00 on 08/30/2014

To have the cells show the correct results for the above formulas, remember to use the correct formatting for worksheet cells, such as; ‘General’, ‘Date’, ‘Time’, or ‘Date & Time’.