DateTime::getDateTimestamp

static function getDateTimestamp(BitrixMainTypeDateTime $date): int
{
	$timestamp = MakeTimeStamp($date);

	if ($timestamp === false)
	{
		$timestamp = strtotime($date);
		if ($timestamp !== false)
		{
			$timestamp += CTimeZone::getOffset() - BitrixMainTypeDateTime::createFromTimestamp($timestamp)->getSecondGmt();
		}
	}

	return $timestamp;
}