The typical perl install might not include DateTime::TimeZone, it's not in Core library. If your users are using it, they need to update it. If you've included it in a local standard site_perl library, you need to update it.

As described above and in parallel threads Daylight Saving, Daylight Savings, most Perl installs will be fine once you have patched the OS which should update the Olson TZ/zoneinfo file that localtime(3) and thus Perl's localtime() use. Sometimes this patches libc, sometimes /usr/share/.../zoneinfo/*, but either way it's updating an Olson TZ file aka zoneinfo.

HP Support Forums have a dst.pl script that uses Perl's localtime() to determine if Zonefile is correct or not. However, I've found it to not work on RHEL3 with Perl 5.8.0.

I'm suspecting that Perl from the RPM was built with GCC2 (glibc2.0, 2.3.2) while rest of RHEL3 is GCC3 (323). So there may be a stealth glibc2 whose stealth Olson needs refresh on my RHEL3. I was hoping someone here would have the answer to that instead of my bringing answers.