CBPCalc::functionDateAdd

private function functionDateAdd($args)
{
	if (!is_array($args))
	{
		$args = [$args];
	}

	$ar = $this->ArrgsToArray($args);
	$date = array_shift($ar);
	$offset = $this->getDateTimeOffset($date);
	$interval = array_shift($ar);

	if (($date = $this->makeTimestamp($date)) === false)
	{
		return null;
	}

	if (empty($interval))
	{
		return $date; // new BizprocBaseTypeValueDateTime($date, $offset);
	}

	// 1Y2M3D4H5I6S, -4 days 5 hours, 1month, 5h

	$interval = trim($interval);
	$bMinus = false;
	if (mb_substr($interval, 0, 1) === "-")
	{
		$interval = mb_substr($interval, 1);
		$bMinus = true;
	}

	static $arMap = ["y" => "YYYY", "year" => "YYYY", "years" => "YYYY",
		"m" => "MM", "month" => "MM", "months" => "MM",
		"d" => "DD", "day" => "DD", "days" => "DD",
		"h" => "HH", "hour" => "HH", "hours" => "HH",
		"i" => "MI", "min" => "MI", "minute" => "MI", "minutes" => "MI",
		"s" => "SS", "sec" => "SS", "second" => "SS", "seconds" => "SS",
	];

	$arInterval = [];
	while (preg_match('/s*([d]+)s*([a-z]+)s*/i', $interval, $match))
	{
		$match2 = mb_strtolower($match[2]);
		if (array_key_exists($match2, $arMap))
		{
			$arInterval[$arMap[$match2]] = ($bMinus ? -intval($match[1]) : intval($match[1]));
		}

		$p = mb_strpos($interval, $match[0]);
		$interval = mb_substr($interval, $p + mb_strlen($match[0]));
	}

	$date += $offset; // to server

	$newDate = AddToTimeStamp($arInterval, $date);

	$newDate -= $offset; // to user timezone

	return new BizprocBaseTypeValueDateTime($newDate, $offset);
}