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:

Setting your rejection filter as DATE CUSTOM >= TODAY + 1 DAYS will reject all leads that have a date in the future.

TODAY's date will be accepted - TOMORROW's date and future dates will be rejected

 
Setting your rejection filter as DATE CUSTOM < TODAY will reject all leads in the past.
 
TODAY and future dates will be accepted - YESTERDAY and further back into the past will be rejected
 

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.