I've just tried this patch against Python 2.4.4, changing the define tested to HAVE_TM_ZONE (in line with the autoconf test AC_STRUCT_TIMEZONE), but it didn't seem to produce the desired result (despite activating the new code in calls to gettmargs):

Python 2.4.4 (#1, Feb 23 2007, 12:37:26)
[GCC 3.3.5 (Debian 1:3.3.5-8ubuntu2.1)] on linux2
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>>> import time
>>> lt = time.localtime()
>>> time.strftime("%Y-%m-%d %H:%M:%S %z", lt)
'2007-02-24 00:45:23 +0000'

The %z output should be '+0100'. According to the mktime man page, the time zone should be set "as though mktime() called tzset()", but a simple C test program revealed that either the tm_gmtoff field remains unset or is set to zero (which is not appropriate on my system).

In other words, mktime does not miraculously restore the time zone information prior to the structure initialisation in gettmargs, at least on my system.