CBPCalc::FunctionIsWorkDay: Bitrix method

      
<?php 
//  CBPCalc :: FunctionIsWorkDay()
//  /dist/bitrix/modules/bizproc/classes/general/calc.php:704

    private function FunctionIsWorkDay($args)
    {
        if (!CModule::IncludeModule('calendar'))
            return null;

        if (!is_array($args))
            $args = [$args];

        $ar = $this->ArrgsToArray($args);
        $date = array_shift($ar);
        $user = array_shift($ar);

        if ($user)
        {
            $date = $this->FunctionToUserDate([$user, $date]);
        }

        if (($date = $this->makeTimestamp($date, true)) === false)
            return null;

        return !$this->isHoliday($date);
    }