I recently found a problem on a php piece of code 
who looks like:

putenv("TZ=$Some_TZ");  // Like "EST5EDT"
$val=  strftime("%Z");
echo "Timezone = ".$val;

It sometimes get the right value, sometimes some "near" garbage
values. Not repeateable (at random under apache).

it looks like that under standard linux(glibc2), all "time" related function
should call "C" function tzset() before first usage.

I see in the source that:  _php_mktime() is calling tzset() #if HAVE_TZSET

the strftime() function need this too (for linux at least)

thanks,
Xtian.