Activity::setDeadlineAction

public function setDeadlineAction(int $activityId, int $ownerTypeId, int $ownerId, string $value): void
{
	$activity = $this->loadActivity($activityId, $ownerTypeId, $ownerId);
	if (!$activity)
	{
		return;
	}

	if(!\CCrmActivity::CheckUpdatePermission($ownerTypeId, $ownerId))
	{
		$this->addError(\Bitrix\Crm\Controller\ErrorCode::getAccessDeniedError());

		return;
	}
	$deadline = $this->prepareDatetime($value);
	if (!$deadline)
	{
		return;
	}

	\CCrmActivity::PostponeToDate($activity, $deadline, true);
}