Repeating date (multiple values) I need to add multiple values to the repeating date field. 

I have to make the schedule for a university classes. So I might have multiple groups with different schedule (different hours for each group) for the same class.

Now it's dificult to assign the schedule for each group on the same node (I don't think it is even posible), but I think at least I could have multiple values on each repeating date, e.g. each thursday at 12:00 and 14:00, and each friday 10:00 and 16:00.

I'm using the latest Drupal 6 and CCK.
I can't use Drupal 7 at the moment for this project, but minor version upgrades can be possible.
You should take a look at the office hours module. While it might not be created for your use case, it allow you to store repeatedly dates for stuff like each friday 10:00-16:00.