What's the output of this script:

<?php
error_reporting( E_ALL | E_STRICT );

echo date_default_timezone_get(), "\n";

echo "time() = " . time() .
    " \nstrftime = ", strftime("%T %Z %z") .
    " \nGMT offset = " . mktime(0, 0, 0, 1, 1, 1970) .
    "\n";
?>

Output of script:

PHP Strict Standards:  date_default_timezone_get(): It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'America/Buenos_Aires' for 'ARST/-2.0/DST' instead in /root/- on line 4
America/Buenos_Aires
time() = 1201827963 
strftime = PHP Strict Standards:  strftime(): It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'America/Buenos_Aires' for 'ARST/-2.0/DST' instead in /root/- on line 9
PHP Strict Standards:  mktime(): It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'America/Buenos_Aires' for 'ARST/-2.0/DST' instead in /root/- on line 9
23:06:03 ARST -0200 
GMT offset = 10800

Do note that I have updated the zoneinfo of the system, and the 
way to define the time zone is now

Amertica/Argentina/Cordoba

I noticed that is some systems the Argentina directory was added,
but the old BuenosAires etc files were not removed in the
America level (BuenosAires, Cordoba, Jujuy, SanJuan, and a couple
others.

John

That was a typo, it must be:

America/Argentina/Cordoba

John

Sorry, but your problem does not imply a bug in PHP itself.  For a
list of more appropriate places to ask for help using PHP, please
visit http://www.php.net/support.php as this bug system is not the
appropriate forum for asking support questions.  Due to the volume
of reports we can not explain in detail here why your report is not
a bug.  The support channels will be able to provide an explanation
for you.

Thank you for your interest in PHP.

You need to install the pecl/timezonedb extension.