Not mentioned above. You could also crate a DateTime object by providing a timestamp as string in the constructor with a leading @ sign.
$dt = new DateTime('@123456789');
$dt->setTimezone(new DateTimeZone('America/New_York'));
echo $dt->format('F j, Y - G:i');
See the documentation about compound formats: https://www.php.net/manual/en/datetime.formats.compound.php