A DST Bedtime Story

My wife works for the U.S. Antarctic program. Often, at work in the Denver office, she checks in with what Jeff Gamet and I are writing over at
the Mac Observer. All last week, she’d been checking his Daylight Saving Time (DST) articles because she has to monitor many computers in Denver as well as at the South Pole.

In Jeff’s summary article about Daylight Saving
Time, he showed a command line technique to make sure the
Mac is properly configured for DST this year.

zdump -v /etc/localtime | grep 2007

But it didn’t give the right results on her Mac. She checked About This Mac, and it said she was running 10.4.8, just as she thought. She knew that Macs had been U.S. DST ready since Mac OS X 10.4.5 and was puzzled for a few minutes.

Then she looked at the Menu Bar clock and realized the problem. Her Mac
is typically set up for the New Zealand time zone, and New Zealand follows
a different cycle for DST.

As an aside, contrary to some SciFi shows, the U.S. Antarctic outpost,
the Amundsen-Scott station, at the South Pole, does not follow Universal Time (UTC) — which some people still refer to as Greenwich Time. (There’s a small technical difference.) The South Pole’s clocks are slaved to New Zealand time because Christchurch, NZ, is the base of operations for the program. So much cargo and people traffic comes and goes through New Zealand that it’s simpler to have the South Pole time set equal to New Zealand time.

Anyway, my wife quickly realized her mistake. The moral of the story
is that sometimes poor software programming makes computers act dumb.
But when the programmers do it right, then the human using
the computer has to be very alert about what’s happening.

So, you can go to bed tonight and know that your Mac will figure it all
out. No matter what time zone you’re in.