Can be reproduced in the demo:

• Open the default document in the radrichtextbox demo
• Activate change tracking (button "Track Changes")
• Make a modification to the document (delete a paragraph)
• Hover your mouse over the delete text: the date in the revision info. has always ":00" for the seconds

In our processes, it is very important to know if a change happened before or after another action. If all the revisions have zero seconds, it's impossible to determine the order of the changes when they happened in the same minute.

This is not a new bug introduce in SP2: it was there in SP1.