I would try a couple of things.

First, give N6 and O6 an unambiguous date/time format.
Like:
mmmm dd, yyyy hh:mm:ss

If the values don't change, then your entries aren't really date and times.
They're just plain old text. You'll want to convert them to real dates/times.

If they do change to that nice format, then check the years. Maybe one of those
10's is 1910 and the other is 2010????

Teri wrote:

I'm trying to write a formula to determine if a delivery is on time. In the
example below, I used =IF(O6<=N6,"Yes","No") and Excel returned "No", but
this shipment was on time. What am I doing wrong?

Column N Column O
Scheduled Delivery Date / Time Actual Delivery Date / Time
25-May-10 05:00 PM 25-May-10 09:00 AM

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Dave Peterson