Document::getDocumentCreateDate

private function getDocumentCreateDate(): ?DateTime
{
	$createTimeField = $this->getDocument()->getFields(['DocumentCreateTime'])['DocumentCreateTime'] ?? null;
	if (is_array($createTimeField) && isset($createTimeField['VALUE']))
	{
		$createTime = $createTimeField['VALUE'];
		while ($createTime instanceof Value)
		{
			$createTime = $createTime->getValue();
		}

		if (is_string($createTime))
		{
			try
			{
				$parsedCreateTime = new DateTime($createTime);
			}
			catch (ObjectException $incorrectDateException)
			{
				$parsedCreateTime = null;
			}

			$createTime = $parsedCreateTime;
		}

		if ($createTime instanceof DateTime)
		{
			// createTime was modified by user, use modified value
			return $createTime;
		}
	}

	return $this->getDocument()->getCreateTime();
}