When\When::findDateRangeOverlap PHP Method

    private function findDateRangeOverlap($startDate, $endDate)
    {
        // Trim to the defined range of this When:
        if ($this->startDate > $startDate) {
            $startDate = clone $this->startDate;
        }
        if ($this->until && $this->until < $endDate) {
            $endDate = clone $this->until;
        }
        return array($startDate, $endDate);
    }