In tzdata2012a the major changes are:

- Chile 2011/2012 and 2012/2013 summer time date adjustments.
- Falkland Islands onto permanent summer time (we're assuming for the
foreseeable future, though 2012 is all we're fairly certain of.)
- Armenia has abolished Summer Time.
- Tokelau jumped the International Date Line back last December 2011
(just the same as their near neighbour, Samoa).
- America/Creston is a new zone for a small area of British Columbia, Canada

A few more minor changes are also included:

- Changes to Canadian 1918 summer time end dates (so it occurred
on a Sunday, rather than Thursday, which is more likely correct.)

Your running version of Time Zone Master should be able to pick up these changes automatically, or manually, depending on your 'Auto Update tz Data' settings.