Daylight Saving Time (DST), the reason your gadgets show the wrong time for half the year, is being extended in the US and Canada next year to start on the second Sunday in March and end on the first Sunday in November. The US tried this before in 1974 as a response to the energy crisis and it was alleged to have saved 10,000 barrels of oil a day and prevented 50 traffic fatalities.
Some software has the daylight saving dates hard-coded and will require an upgrade. For most Informix DBAs this should not be a problem since IDS gets its time from the operating system. As long as your operating system changes its time on the right date the transition should be no different to usual. (Remember to restart IDS after installing relevant OS patches.) Java has some hard-coded dates though, so if you use Java applications which perform date calculations you need to think about upgrading JRE to the latest versions (Australians had a similar problem in 2006).
If you have Java UDRs which call"get time of day" functions then you may need to upgrade IDS in order to get a fixed JRE. This IBM Alert describes which versions are affected and what you need to do: Action Required: Changes to daylight saving time (DST) in the U.S. and Canada affect IBM Informix Dynamic Server. The IIUG also has a page dedicated to this topic with additional information: March 2007 Daylight Savings Time Change Information. If your JRE is an IBM one and has JTZU you can fix the problem without updating, see the IBM Time Zone Update Utility for Java (JTZU).
The central IBM website for DST changes is Daylight Saving Time alert - this includes a FAQ and will change as new updates are added.
If you use other IBM software you may need to care more. Here are some of the relevant links..
Application Servers: Possible implications if one does not apply the Daylight Saving Time fixes
DB2: Actions required: Changes to daylight saving time (DST) in the U.S. and Canada affect IBM® DB2® products
Lotus Notes and Domino: Daylight Saving Time (DST) 2007 information for Lotus Notes and Domino
Lotus Sametime: Daylight Saving Time (DST) 2007 information for Lotus Sametime
Websphere: URGENT Actions Required: Changes to Daylight Saving Time will affect IBM WebSphere Application Server and its associated Operating Systems.
Websphere Everyplace Connection Manager: Daylight Saving Time (DST) 2007 information for WebSphere Everyplace Connection Manager
Websphere MQ: US Daylight Saving - How changes to daylight saving time affect WebSphere MQ, WebSphere MQ Express and WebSphere MQ Everyplace
Update: Bobby Woolf added a comment pointing out his Websphere blog entry Daylight Saving Time and Java which has some useful information on this topic, including a link to the Sun Developer Network article about extended DST.
Update #2: Windows users and developers should refer to these Microsoft documents: Preparing for daylight saving time changes in 2007, FIX: Windows-based applications that use the TZ environment variable may not work as expected because of changes to DST, FIX: Visual C++ .NET 2003 C runtime daylight saving time 2007 update for the TZ environment variable problem.