If you set a DEFAULT_TIMEZONE, the collision detection
code may always detect a collision (in 0.7.1).

You can reproduce this by setting up a demo tracker,
setting the DEFAULT_TIMEZONE to -4, creating an issue
and then trying to change something in that new issue.

I believe the following patch fixes the problem, though
I don't know if it's the right way to fix it.  (This
fixes the check; an alternative might be to fix the
generation of @lastactivity parameter when it is
generated...)

--- actions.py~ Thu May 13 20:55:03 2004
+++ actions.py  Thu May 13 20:49:58 2004
@@ -469,7 +469,8 @@
 
     def lastNodeActivity(self):
         cl = getattr(self.client.db, self.classname)
-        activity = cl.get(self.nodeid,
'activity').local(0)
+       tz = self.client.db.getUserTimezone()
+        activity = cl.get(self.nodeid,
'activity').local(tz)
         activity.second = int(activity.second)
         return activity

Logged In: YES 
user_id=6405

I've applied a better change which also fixed the date HTML property 
local() method so it could override the user's timezone. 
 
Thanks for the sleuthing though!