how to format atom date time

strtotime is a wonderful function for converting date formats to Unix timestamps.

This will give you what you're after:

date('my format here', strtotime('2009-11-04T19:55:41Z'));

What about

\DateTime::createFromFormat(\DateTime::ATOM, $AtomDate); // converting Atom date to object

or

date(\DateTime::ATOM, $timestamp); // formatting timestamp to Atom time

or both

$dto = \DateTime::createFromFormat(\DateTime::ATOM, $AtomDate);
date('d-M-Y H:i:s', $dto->getTimestamp()); // formatting Atom date to anything you want

or even better

$dto = \DateTime::createFromFormat(\DateTime::ATOM, $AtomDate);
$formattedDate = $dto->format('d-M-Y H:i:s');

or with time zone (as mentioned in comments)

$dto = \DateTime::createFromFormat(
    \DateTime::ATOM,
    $ticketUpdatedAt,
    new \DateTimeZone('UTC')
);
$ticketUpdatedDate = $dto->format('Y-m-d H:i:s');

Try using strptime:

$date = strptime($str, "Y-m-d\TH:i:s\Z");