When\When::occursOn PHP Method

    public function occursOn($date)
    {
        if (!Valid::dateTimeObject($date)) {
            throw new \InvalidArgumentException("occursOn: Accepts valid DateTime objects");
        }
        // breakdown the date
        $year = $date->format('Y');
        $month = $date->format('n');
        $day = $date->format('j');
        $dayFromEndOfMonth = -((int) $date->format('t') + 1 - (int) $day);
        $leapYear = (int) $date->format('L');
        $yearDay = $date->format('z') + 1;
        $yearDayNeg = -366 + (int) $yearDay;
        if ($leapYear) {
            $yearDayNeg = -367 + (int) $yearDay;
        }
        // this is the nth occurrence of the date
        $occur = ceil($day / 7);
        $occurNeg = -1 * ceil(abs($dayFromEndOfMonth) / 7);
        // starting on a monday
        $week = $date->format('W');
        $weekDay = strtolower($date->format('D'));
        $dayOfWeek = $date->format('l');
        $dayOfWeekAbr = strtolower(substr($dayOfWeek, 0, 2));
        // the date has to be greater then the start date
        if ($date < $this->startDate) {
            return false;
        }
        // if the there is an end date, make sure date is under
        if (isset($this->until)) {
            if ($date > $this->until) {
                return false;
            }
        }
        if (isset($this->bymonths)) {
            if (!in_array($month, $this->bymonths)) {
                return false;
            }
        }
        if (isset($this->bydays)) {
            if (!in_array(0 . $dayOfWeekAbr, $this->bydays) && !in_array($occur . $dayOfWeekAbr, $this->bydays) && !in_array($occurNeg . $dayOfWeekAbr, $this->bydays)) {
                return false;
            }
        }
        if (isset($this->byweeknos)) {
            if (!in_array($week, $this->byweeknos)) {
                return false;
            }
        }
        if (isset($this->bymonthdays)) {
            if (!in_array($day, $this->bymonthdays) && !in_array($dayFromEndOfMonth, $this->bymonthdays)) {
                return false;
            }
        }
        if (isset($this->byyeardays)) {
            if (!in_array($yearDay, $this->byyeardays) && !in_array($yearDayNeg, $this->byyeardays)) {
                return false;
            }
        }
        // If there is an interval != 1, check whether this is an nth period.
        if ($this->interval > 1) {
            switch ($this->freq) {
                case 'yearly':
                    $start = new \DateTime($this->startDate->format("Y-1-1\\TH:i:sP"));
                    $sinceStart = $date->diff($start);
                    $numPeriods = $sinceStart->y;
                    break;
                case 'monthly':
                    $start = new \DateTime($this->startDate->format("Y-m-1\\TH:i:sP"));
                    $sinceStart = $date->diff($start);
                    $numYears = $sinceStart->y;
                    $numMonths = $sinceStart->m;
                    $numPeriods = $numYears * 12 + $numMonths;
                    break;
                case 'weekly':
                    if (isset($this->bydays)) {
                        $weekStartDate = self::getFirstWeekStartDate($this->startDate, $this->wkst);
                    } else {
                        $weekStartDate = $this->startDate;
                    }
                    $sinceStart = $date->diff($weekStartDate);
                    $numPeriods = floor($sinceStart->days / 7);
                    break;
                case 'daily':
                    $sinceStart = $date->diff($this->startDate);
                    // Note we "expanded" startDate already.
                    $numPeriods = $sinceStart->days;
                    break;
                case 'hourly':
                    $sinceStart = $date->diff($this->startDate);
                    // Note we "expanded" startDate already.
                    $numDays = $sinceStart->days;
                    $numHours = $sinceStart->h;
                    $numPeriods = 24 * $numDays + $numHours;
                    break;
                case 'minutely':
                    $sinceStart = $date->diff($this->startDate);
                    // Note we "expanded" startDate already.
                    $numDays = $sinceStart->days;
                    $numHours = $sinceStart->h;
                    $numMinutes = $sinceStart->i;
                    $numPeriods = 60 * (24 * $numDays + $numHours) + $numMinutes;
                    break;
                case 'secondly':
                    $sinceStart = $date->diff($this->startDate);
                    // Note we "expanded" startDate already.
                    $numDays = $sinceStart->days;
                    $numHours = $sinceStart->h;
                    $numMinutes = $sinceStart->i;
                    $numSeconds = $sinceStart->s;
                    $numPeriods = 60 * (60 * (24 * $numDays + $numHours)) + $numMinutes + $numSeconds;
                    break;
            }
            if ($numPeriods % $this->interval == 0) {
                return true;
            } else {
                return false;
            }
        }
        return true;
    }