The webpart column "calculated" can be quite useful...

http://office.microsoft.com/en-us/sharepointtechnology/HA101054791033.aspx#2

http://www.theblackson.com/_layouts/help.aspx?lcid=1033&cid0=MS.WSS.manifest&tid=MS.WSS.HA01160981

http://martijnmolegraaf.blogspot.com/2009/01/using-today-in-calculated-formula.html

DATEDIF(start_date,end_date,unit)

"Y" The number of complete years in the period. "M" The number of complete months in the period. "D" The number of days in the period. "MD" The difference between the days in start_date and end_date. The months and years of the dates are ignored. "YM" The difference between the months in start_date and end_date. The days and years of the dates are ignored "YD" The difference between the days of start_date and end_date. The years of the dates are ignored.

=DATEDIF(older_column,more_recent_date,"Y") -> output should be single line of text or number

Note that if the more recent date column is put first or a column lacks data it will return #NUM!

First create the older_column (date) and Today column (any type).

Then create the caluclated column with the following formula:

=DATEDIF(older_column,Today,"D") (output can be number or single line of text)

Then delete the Today column.

Now your formula will calculate t

Note that if you try to modify the calculated column formula afterwards you'll received the Error "Calculated columns cannot contain volatile functions like Today and Me."

(So recreate the Today column, make your changes to the formula, then delete Today again)