If you're looking for a filter or delivery rule operator which allows you to set dynamic rulesets such as those shown below, then you're in luck! 

Only accept leads where the opt-in date is from the last 7 days

or

Reject all leads where the DOB is in the future

The Custom operator can use any of the below parameters -

Time parameters

TODAY
NOW
SEC (also accepts SECOND)
MIN (also accepts MINUTE)
HOUR
DAY
WEEK

Inequality statements

<=
>=
<
>
==
!=
=

Additional statements

(
)
+
-
/
*

Filter examples

 Do not accept leads into your campaign with an Opt In Date more than 2 years in the past:

Do not deliver leads with an DOB in the future:

If you're having issues writing a filter which does exactly what you need, raise a ticket with us and we'll do our best to help out.