Among the new features of Windows 7 is the super calculator has many functions, and among these features one of them is the ability to calculate the difference between two dates.
In the View menu, select “Date Calculation” :
Alternatively, you can use CTRL + E from the keyboard.
The function to calculate between two dates will appear. Click the small calendar beside the “From” to select the start date, with the arrows you can change the month, click on the day of your choice and select the date of the end :
Then click Calculate, the difference between two dates result will be shown: