I submitted a bug report on this and it appears it is a known problem.
-Tony
This is a follow up to Bug ID# 6545953. After further investigation it has been determined that this is a known issue, which is currently being investigated by engineering. This issue has been filed in our bug database under the original Bug ID# 6478275. The original bug number being used to track this duplicate issue can be found in the State column, in this format: Duplicate/OrigBug#.
Thank you for submitting this bug report. We truly appreciate your assistance in helping us discover and isolate bugs.
Best Regards,
Kit Cheung
Apple Developer Connection
Worldwide Developer Relations
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Bug ID #: 6545953
Bug Title: Migration Assistant corrupts timezone selection when migrating from 10.4 to 10.5
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<GMT31-Jan-2009 06:33:55GMT>
When using the Migration Assistant to migrate from 10.4 to 10.5 the /etc/localtime file is brought across incorrectly. It should be kept as a link but instead the directory it links to is copied across. This leaves it as a directory rather than a link to /usr/share/zoneinfo/country/tz. This causes the Date Time preferences panel to be unable to change the time zone, leaving it stuck as GMT.
Disk Utility does correctly report this problem, but does not succeed in repairing the problem (it actually reports success in repairing all problems).
There is more information on this issue discussed at:
http://discussions.apple.com/thread.jspa?messageID8340794
There seem to be two fixes required:
1. Migration Assistent should preserve the /etc/localtime as a symbolic link when migrating from 10.4
2. Disk Utility should delete /etc/localtime if it is a directory and make it a symbolic link to /usr/share/zoneinfo/US/Pacific to default it to USA PST. The the user can then change the time zone using the Date Time preference pane.