How to properly set "0000-00-00 00:00:00" as a DateTime in PHP

php symfony datetime doctrine-orm

PHP Snippet 1:

$entEmail = new Email();
$entEmail->setViewedAt(null);

PHP Snippet 2:

$Date = date('Y-m-d H:i:s');

PHP Snippet 3:

date_default_timezone_set('America/New_York');
$date = date('Y-m-d H:i:s');

$entEmail = new Email();
$entEmail->setViewedAt( $date );

PHP Snippet 4:

date_default_timezone_set('America/New_York');

$entEmail = new Email();
$entEmail->setViewedAt( date('Y-m-d H:i:s') );