sunnysideup / silverstripe-calendar

        // 1) Research of the week

        $firstDate = mktime(0, 0, 0, 1, 1, $year);

        while (date('W', $firstDate) != 1) {

            $firstDate = mktime(0, 0, 0, date('n', $firstDate), date('j', $firstDate) + 1, date('Y', $firstDate));

        }

        while (date('W', $firstDate) < $week) {

            $firstDate = mktime(0, 0, 0, date('n', $firstDate), date('j', $firstDate) + 7, date('Y', $firstDate));

        }

        while (date('W', $firstDate) != 1) {

            $firstDate = mktime(0, 0, 0, date('n', $firstDate), date('j', $firstDate) + 1, date('Y', $firstDate));

        }

        while (date('W', $firstDate) < $week) {

            $firstDate = mktime(0, 0, 0, date('n', $firstDate), date('j', $firstDate) + 7, date('Y', $firstDate));

        }

        // 2) Research of the first day of the week

        while (date('Y', $weekFirstDate) < $year || (date('Y', $weekFirstDate) == $year && date('n', $weekFirstDate) <= $month)) {

            $weekMonday = $weekFirstDate;

            while (date('N', $weekMonday) != 1) {

                $weekMonday = mktime(0, 0, 0, date('n', $weekMonday), date('j', $weekMonday) + 1, date('Y', $weekMonday));

            }

            $week = date('W', $weekMonday);

            $yearOfWeek = date('Y', $weekMonday);

            if ($month == 1) {

        $lastDate = $this->getWeekStartDay($day, $month, $year);

        while (date('N', $lastDate) != $this->dayStart) {

            $lastDate = mktime(0, 0, 0, date('n', $lastDate), date('j', $lastDate) - 1, date('Y', $lastDate));

        }

        while (in_array(date('N', $lastDate), $this->daysRemoved)) {

            $lastDate = mktime(0, 0, 0, date('n', $lastDate), date('j', $lastDate) + 1, date('Y', $lastDate));

        }

        while (date('N', $lastDate) != $this->dayStart) {

            $lastDate = mktime(0, 0, 0, date('n', $lastDate), date('j', $lastDate) - 1, date('Y', $lastDate));

        }

        while (in_array(date('N', $lastDate), $this->daysRemoved)) {

            $lastDate = mktime(0, 0, 0, date('n', $lastDate), date('j', $lastDate) + 1, date('Y', $lastDate));

        }

        for ($i = 0; $i < $this->number; $i++) {

            $datesGroup = array();

    {

        $date = mktime(0, 0, 0, $month, $day, $year);

        while (date('N', $date) > 1) { // It means that the 1st day of this week is not Monday

            $date = mktime(0, 0, 0, date('n', $date), date('j', $date) - 1, date('Y', $date));

        }

        return $date;

    }