How to Calculate Days in Excel 2007

1. Open a new blank Excel spreadsheet.
2. Place a date in cell A1. Use the format mm/dd/yyyy and make sure the date is the year 1900 or later. For this example, you could use '07/04/2011.' In an existing spreadsheet, the format of the cell may not be 'Date.' To change the format to 'Date,' click 'Format/Cells...' and select the Number tab and then click 'Date' under 'Category:.'
3. Place a date in cell A2. For this example, you could use '07/24/2010.'
4. Type the following formula in cell A3: '=A1-A2' then click 'Enter.' Cell A3 will contain the number of days between the two dates. In this example, the answer will show 365. If cell A3 shows a date instead, change the cell format to 'Number' and select 'Format/Cells...' Click the Number tab and then select 'Number' under 'Category.'