Primary Key using date fields - ignores time part?

I have a table that contains data, and I'm now trying to define a new primary key. One of the fields in the key is a date type. Several rows have the same date, but the time portion of the field is different. It seems that Oracle does not look at the time, and tells me it can't create the key because it would be violated by the data. Can I force it to look at the entire content of the column?

Thanks Received on Thu Sep 04 1997 - 00:00:00 CDT