Q: "If we updated for this [US and Canadian daylight saving time] change this spring, we should be covered for the fall time change, correct?"
A: Generally, the answer is yes. As noted here, it depends: we recommend that companies review their specific situation. Companies that do not have a presence in an affected time zone may find that no DST updates are required. However, Microsoft strongly recommends that customers apply the time zone updates for all affected products. There are a couple of reasons for this:
First, customers may have users who travel to an affected time zone, and as such, their applications could be affected by not having the current time zone updates installed on their client machines.
Second, applying the current DST updates to all machines and applications keeps their environment up-to-date and consistent with worldwide changes. This could be important when communicating with another end user or company in an affected time zone, or where different IT environments come together and coexist.
Overall, Microsoft strongly recommends DST patch installation on all affected systems, devices and applications to ensure consistency with the world’s current time zone information. Customers should review the updates available and posted at http://support.microsoft.com/gp/dst_prodlist for the latest and updated information of Microsoft products affected by daylight saving time, as well as the main DST and TZ page at http://www.microsoft.com/dst2007.
Customers who need the latest updates for the recently-added and revised countries (new time zone rules for Jordan and New Zealand, for example), should get the latest update. Consumers may update their PCs by visiting Microsoft Update at http://www.update.microsoft.com/. Network managers and sysadmins can get the latest Windows OS update (KB 933360) as an "Update Rollup" via WSUS as noted in this post.
Again, there are scenarios where updates and patches are not required, but Microsoft strongly recommends DST patch installation on all affected systems, devices and applications to ensure consistency with the world’s current time zone information.