I do not open attchements, so the following is just my guess.
If you have two values:
Oct 28 2011 10:30
Oct 28 2011 10:40
And, you format it as date:
You get two "values of the same date" because the undelying data is different. To make it "real" date, you have to use integer part of your field as date, and fraction part as time:
date(floor(<datetimefield>)) as Date
time(frac(<datetimefield>)) as Time