Bug #3977 refers to this problem as well (can use that script for bug producibility).

I've tracked this down to a difference between "localtime" and "localtime_r"
(and probably most of the reentrant functions).  The following excerpt from glibc-2.1.3/time/tzset.c

578   /* Update internal database according to current TZ setting.
579      POSIX.1 8.3.7.2 says that localtime_r is not required to set tzname.
580      This is a good idea since this allows at least a bit more parallelism.
581      By analogy we apply the same rule to gmtime_r.  */

It seems that glibc's implementation of thread-safe is to skip calling tzset() internally to set the timezone.  As a result, my PHP4 appears to ignore putenv("TZ=<whatever>").

Possible solutions: 1) Use the new PHP4 php_<funct>_r functions defined in reentrancy.c, or 2) call tzset() externally before calling localtime_r or gmtime_r.  I tried both solutions with the test script from bug #3977 and both solutions appear to work.