I just posted a dozen videos covering features of Excel 2010. Just click the Free Excel Videos link on the right side or on top. These are also available as a channel on YouTube. I made all these videos for Lynda.com.
Between the Sheets — Excel podcast episode 31: Excel’s secret DATEDIF function
A quick and simple way of finding the number of days, months or years between two dates is Excel’s secret DATEDIF function. When you type it in a worksheet, there’s no popup syntax help to indicate the function exists.