Conversion to 8.3

Greetings:

I am converting our application from 7.4.19 to 8.3.1. In the old scheme of
things, I was generating an interval between two timestamps and evaluating
the interval string in another set of trigger code. I was doing the
following:
IF new.ontime IS NOT NULL AND new.ontime ~* 'ago' THEN
.
.
END IF;
With the new casting rules, this doesn't work. How can I determine if this
on-time value is "ago", that is, the shipment is late?

Thanks for any help you can give...
--
Terry Lee Tucker
Turbo's IT Manager
Turbo, division of Ozburn-Hessey Logistics
2251 Jesse Jewell Pkwy NE
Gainesville, GA 30501
Tel: (336) 372-6812 Fax: (336) 372-6812 Cell: (336) 404-6987
terry(at)turbocorp(dot)com
www.turbocorp.com