how to calculate the 4 days before date of the target date

Question

i have two dates

ValidFrom : 20-04-2010

validTo : 02-05-2010

i need to know 4 days(date) before the validity expire .how to calculate the 4 days before date of the validity expire date 02-05-2010

Answer 1

var dt = new DateTime(2010, 5, 2);
var fourDaysBefore = dt.AddDays(-4);

If that's not what you mean, you're going to have to be much more specific.

Answer 2

I can't really tell what the context of the question is but this is one way to do it if you were trying to do it in mysql.

SELECT ADDDATE('2010-05-02', INTERVAL -4 DAY);