I'm rather confused by your bug: DateTimeZone::listIdentifiers() doesn't list offsets, and the code that does appears to be correct on any recent PHP version:

<?php
$tz = new DateTimeZone("America/Caracas");
var_dump($tz->getOffset(new DateTime()) / 3600);
?>

outputs float(-4.5), which lines up with your bug.

What version of PHP are you running, what does phpinfo() list the Olson Timezone Database Version as, and what do you get when you run the above code?

Sorry for opening the ticket with so little information, and thank you very much 
for your reply. I was using a third party library fro listing all timezones along 
with their offsets and while all seemed right, this one was listed as -5.5, I 
tested the code you provided and in fact -4.5 is returned. I guess I'll have to 
fix the library instead.

Again, thanks a lot for your help and sorry for wasting your time :)

Bumping to bogus per last comment.