The Pencil Guy: Hourann's illogical blog

Now to actually change the clocks …

So unless you want to manually set your computer’s clock (which breaks auto-update by NTP), or change your timezone to Osaka (which might confuse location-based services), our politicians have given Perth’s IT community an entire working week to figure out how to get computers to change their time automatically on December 3. And it’s not like this is a trivial issue — wrong time breaks all sorts of things, from Kerberos to log files to sessions in Web services.

Microsoft have kindly released a patch (which was unusually prompt of them) that makes things happy and good for Windows users … though it’s still a hassle if you’ve got hundreds of boxes to update.

In the Unix world, one must play with zoneinfo files, which isn’t impossibly difficult, but does take a bit of work. Fortunately Matt @ UCC has done just this.

Do that note his instructions omit the need to replace /usr/share/zoneinfo/Australia/West as well as /usr/share/Australia/Perth … both files should be identical. In addition, be aware that your average Linux system has several copies of the zoneinfo database generated from the main one. In particular, Java, the Perl DateTime module, and libical have their own copies, and if you have software that depends on those (e.g. Evolution, or Korganizer) then they often create their own copies. Running locate Australia/Perth is a wise move.

Sadly, on Mac OS X, changing zoneinfo files isn’t enough … there is a second timezone data store attached to the International Components for Unicode, built from the zoneinfo data and used in most GUI applications (to make multilingual date display easier). Unfortunately this makes the process of changing the timezone horribly difficult even if you’re an OS X nerd, with the only hope being the 10.4.9 update from Apple — not due till next year.

So Mac users are out in the cold for now. Though of course, our wonderfully competent State politicians don’t concern themselves with such trivial matters.

Meanwhile, in happier news, Flickr’s new Camera Finder is an awesome idea. It warms my heart that there are people out there still using my old Fuji :-)

Updated 24/11: learnt about 10.4.9 and Mark’s quite detailed OS X assessment, and discovered the other Linux timezone files.

  1. Cool! Thanks for that. I naturally assumed that NTP would take care of it. How it was going to take care? I dunno!

  2. If only things were so easy!

    NTP sends time data as UTC, and your computer converts that to the local time zone. This is why, for instance, every Windows box in the world can use the same NTP server (

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