Samigo unsure as to whether it's using client time zones or server time zones in publishing content.
This works looking at sakai-stable from the UK - it won't work unless you're have different time zones.
1) Create a quiz
2) Publish it, setting the available date to today using the pop-up calendar. It will supply today's date and time as specified by the client computer - e.g. 11/17/2005 03:03:05 PM . The administrator expects that to mean it will appear instantly.
1) Log on and look for that quiz. It won't have appeared yet because the UK time is ahead of the time where the server is located.