The Daylight Saving Time Update for Mac OS X 10.4.8 updates your Daylight Saving Time and time zone rules to the latest available information as of January 7, 2007. This includes the new start and end dates for Daylight Saving Time in the province of Alberta, Canada, as well as recent time zone updates in Australia, Brazil, and other countries. The new 2007 Daylight Saving Time rules for the US and the rest of Canada are already installed as of Mac OS X 10.4.5 or later (see this article for more information).
This update requires Mac OS X 10.4.8 or Mac OS X Server 10.4.8. It can be installed on both Intel- and PowerPC-based Macs. It is available via automatic Software Update, or as a standalone download. You only need to use one of these methods to update your computer.
For more information about the 2007 Daylight Saving Time changes and other Apple Daylight Saving Time updates, see this article.