Symptom: Subversion (svn) $LastChangedDate$ does not get updated when svn commits are made, leading to the Last Updated text on the webpages not being updated.
Problem: Linefeed in keyword. The files concerned had created (i.e. copied from existing files under svn) with a $LastChangedDate: <date>$ which was very long and wrapped by the text editor. These were then checked into subversion without the LastChangedDate keyword set. Once the broken date was in the repository it was never updated because the final $ was on a separate line to the rest of the keyword.
Fix: remove the ": <date>" from the $LastChangedDate: <date>$
Alternate fix: remove the spurious linefeed from the LastChangedDate field
Solution: None of the subversion keywords need to contain any text at all on commit, since they are automatically filled in at checkout by the client. Thus new files can be created with $LastChangedDate$ rather than $LastChangedDate: <date>$