"So, the point here is that for some users on some builds of our
nightlies, the timezone upgrade will fail.  It will cause the
application to throw and it will no longer startup properly. "

So my question before I upgrade to a nightly with this fix in:

I have backed-up my calendars, but what should I do when the above
described scenario occurs? Can I still startup Thunderbird? If so,
should I un-install Calendar, re-install it and create new calendars and
import my backups?
If TB does not start at all, what do I do than?

Warning people is great, but without telling them what can be done to
fix the problem if it occurs is not really helpfull. (or maybe it is
just me and all other nightly testers already know how to recover from
such a problem.)

Marcel