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<?php $dt = new DateTime('2015-01-01 00:00:00+00:00'); var_dump($dt->format('c')); var_dump($dt->modify('+1 s')->format('c')); $dt = new DateTimeImmutable('2015-01-01 00:00:00+00:00'); var_dump($dt->format('c')); var_dump($dt->modify('+1 s')->format('c'));

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