Thanks for your help, I didn't know about that. The problem is not solved though. Let me explain a bit further:
I have 2 Date fields. One is called "Calendar Date", and the other is called "Action Date". Calendar Date is the date the subscription was purchased. Action Date is the date in which the user did something to his subscription (i.e. cancel it). I want to see subscriptions that were done a particular action (ID 12) in the last 7 days (no matter when the subscription has purchased).