Ever wonder how you can calculate the age of the list items in SharePoint?  The Today() function is not allowed in calculated fields, so what's the trick?

1. Go to the list where you want to calculate age of the items e.g. Task List
2. Click Settings => List Settings and create a new column and name it e.g. "Today", There is no need to select any specific type for this column (Just type the name of the column and click "OK" at the bottom)
3. Create one more column and name it e.g. "Age in Days". Select "Calculated(calculation based on other columns)" type and provide formula using "Today" column which you created in step 2 e.g. I have entered
=[Today]-[Created]. Select "number" for the data type and 0(zero) in "Number of Decimal places". So basically it will calculate difference between today’s date and date the item was created.
4. After 3rd step, remove "Today" column, which you have created in step 2. When you remove Today column, SharePoint automatically refers "Today" (which has been deleted now) as the today’s date in the formula calculation.
5. Go back to Task List and it should display the number of days under the "Age in Days" column of each items in Task List.


...thanks to Explore SharePoint @:
http://www.exploresharepoint.net