/**
* Get the VAT value for some unix timestamp
* @param int $timestamp the time to get VAT for
* @return float the VAT at the given time (0-1)
*/
protected static function getVATAtDate($timestamp)
{
if (!isset(self::$vatAtDates[$timestamp])) {
self::$vatAtDates[$timestamp] = Billrun_Util::getVATAtDate($timestamp);
}
return self::$vatAtDates[$timestamp];
}