Instructions

1

Open a new workbook in Microsoft Excel. Type the start date in a cell. For example, type 12/22/1982 in cell A1.
2

Type the end date in another blank cell. As an example, type 6/8/2009 as the end date in cell A2.
3

Click on a blank cell and type "=DAYS360(start_date, end_date, method)". In the example above, the formula would be =DAYS360(A1,A2), which returns 9526 days. The formula assumes 360 days in a year (12 months with 30 days). The method argument specifies the calculation method. It can be left blank when working with U.S. dates, but must be set to TRUE when working with European dates.