How to only show date if time is not defined?

I am using Drupal 6.20 and Calendar 6.x-2.4, and overall I am very happy with it.

I have an issue I can't figure out how to solve. I am using calendar for showing events and news, and generally that works fine. However, on our site, the time for some event will only be given as a date, whereas for others there will both be date and time (hours:minutes).

In the cases where the time is not defined, and only the date is given, my events are shown as (example) 2011-01-28 00:00. I want to be able to NOT show the 00:00 and in that case only show 2011-01-28, while still show times when they are defined (like 2011-01-28 12:30).

So, if 2011-01-28 00:00 I want to show 2011-01-28

and

if 2011-01-28 12:30 I want to show 2011-01-28 12:30

Is there a way to do this? I have been playing around with fields and filters and have not gotten what I want.

Or, alternatively, is there a way to not have the time 00:00 added to the date when times are not given (I realise this may be more of an issue with how my datetime type is defined, but I found nothing obvious to change there either)