Can a table do calculations such as add 25 days to a set date in another field ?

Calculations would be preformed in Queries rather than tables. But you can base a query on a table, add the calculation, then base the form or report on the query.

You don't do calculations in Tables. You do calculations in queries, and on forms and reports.

You don't need to store the calculated value in the table, since it can be recalculated whever it is needed.

-AJ