Add/subtract cells in UITable Xcode

[Ouija]

In my app, I have a UITableView with 3 cells, if the user selects one of the top two cells, they can change the value using a UIDatePicker to make it say for example 'November 11, 2011'. My question is, is there a way to subtract the dates from the first cell to the second one? Like the user inputs November 11, 2011 into the first cell, and in the second cell inputs November 11, 2012, how can I get the 3rd cell to say, 1, or 1 year?

Thanks!

[keeshux]

Keep an NSDate-based data source for the picker, then use NSCalendar/NSGregorianCalendar to compute the date difference.