Quick question on version number

Hi Folks, I was taking a look at a Tomcat 5.0.30 server for a client and checked out the security pages at tomcat.apache.org for updates and such. I had a quick question about the '.SVN' portion of the label Fixed in Apache Tomcat 5.5.25, 5.0.SVN on the security pages for 5.x. What is

Determining a version's release date

Greetings all, What is the most reliable and accurate way of determining the release date for a Tomcat version, e.g., Tomcat 4.0.2 ? Wikipedia doesn't seem to have a full list. Thank you, Norman