While modifying Datetime with the timezone, the user should be aware that changing the timestamp using "@".\time() is not the same as changing the timestamp using setTimestamp().

$now = new \DateTimeImmutable('August 30, 2023 09:00:00 GMT+01');
$origin = $now->getTimestamp(); // 1693382400
$usingAt = $now->modify('@'.$now->getTimestamp())->getTimestamp(); // 1693378800
$usingSetTimestamp = $now->setTimestamp($now->getTimestamp())->getTimestamp(); // 1693382400

var_dump($usingAt === $origin); // false
var_dump($usingSetTimestamp === $origin); // true