IT Support Small Medium Business

As early as 2005, tzdata package on Linux had been updated to accommodate the coming DST changes in North America passed by US Congress in 2004. For example, CentOS 4 (RHEL 4) has such applied changes in its 2005m version of tzdata package. For your convenience, I compiled locally on this site a list of tzdata RPM packages for various RHEL/RHL/CentOS/Fedora Core linux.

For ease of mind, it’d be nice to verify the tzdata is indeed effective for the proposed DST changes on mission critical systems. Here is a simple harmless how-to for Linux taking advantage of the ubiquitous date command.

One simple one is to use the ‘date’ command, which has a ‘-d’ switch to specify any arbitrary date or ‘-f’ switch to test a list of date time strings. To test whether the cut-off date of March 11 and Nov 4 are covered, I did the following on a Fedora Core 6/i386 server:

———x——cutover.timestamp ———–

2007-03-11 01:59:00
2007-03-11 03:00:00
2007-11-04 01:59:00
2007-11-04 02:01:00

———x——cutover.timestamp ———–

$ date -f cutover.timestamp

Sun Mar 11 01:59:00 EST 2007
Sun Mar 11 03:00:00 EDT 2007
Sun Nov 4 01:59:00 EDT 2007
Sun Nov 4 02:01:00 EST 2007

You can also test one datetime string using the ‘-d’ switch,

$ date -d “2007-03-11 03:00:02″
Sun Mar 11 03:00:02 EDT 2007

This means Fedore Core 6/i386 is ready for the coming 2007 DST changes. EDT starts on 2007-03-11 02:00 am and ends 2007-11-04 02:00am. If your system is not EST/EDT, the output may vary. For north American systems, you should see the ‘S’ -> ‘D’ -> ‘S’ changes though. The same test works the same on CentOS 4.1/i386 through CentOS 4.4/i386 systems.

This only guarantees system applications that use the tzdata as provided by the operating systems. Other applications may vary fortheir readiness. For example,

• The JAVA application is not ready for the proposed DST changes. JRE/JDK needs to be updated to JDK-1.5.0_06 at least for JDK 1.5.0 series. If you worry about API change or incompatible bugfix in the newer JDK, you could extract the tonezone from the up-to-date JDK and ‘patch’ your working JDK installation. Here is an excellent article from Java World.
• Research In Motion’s blackberry (firmware version 4.2.0 and earlier) . RIM has compiled a good list of information  on how to update blackberry handheld as well as the BES (Blackberry Enterprise Solution) servers. Notices were sent out to its partners for the coming DST changes. Carrier like T-mobile and Cingular had put out their notices as well.
• RDBMS vendors had put out notices as well. I know Sybase and Oracle did. If nothing else, the database engine may have to be restarted to effect the timezone database updated at the operating systems level.
• All home-grown applications, be it for internal use, off-shelf sales, or ASP, or SaaS purposes.
• Every Other components of your application portfolios.

A true verification should be run, wherever applicable and affordable, by setting the time on the Linux servers (date MMDDhhmm[[CC]YY][.ss]]. Example ‘date 031101582007‘) forward to March 11 before and after the cut-off at 02:00 am EST. Use of date/time functions in all application components should be identified and compiled to a list ready for comparison and verification.

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