CTimeManUser::isEntryValid

public function isEntryValid($action, $timestamp)
{
	global $APPLICATION;

	$arSettings = $this->GetSettings();

	if (!$arSettings['UF_TM_FREE'] && $timestamp !== false)
	{
		// $timestamp is in server time yet
		if (abs(time() - $timestamp) > $arSettings['UF_TM_ALLOWED_DELTA'])
		{
			$APPLICATION->ThrowException('Time was changed manually', 'TIME_CHANGE');
			return false;
		}
	}

	return true;
}