Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/Financial.php
private static function daysPerYear($year, $basis = 0)
    {
        switch ($basis) {
            case 0:
            case 2:
            case 4:
                $daysPerYear = 360;

                break;
            case 3:
                $daysPerYear = 365;

                break;
            case 1:
                $daysPerYear = (DateTime::isLeapYear($year)) ? 366 : 365;

                break;
            default:
                return Functions::NAN();
        }

        return $daysPerYear;
    }
private static function daysPerYear($year, $basis = 0)
    {
        switch ($basis) {
            case 0:
            case 2:
            case 4:
                $daysPerYear = 360;

                break;
            case 3:
                $daysPerYear = 365;

                break;
            case 1:
                $daysPerYear = (DateTime::isLeapYear($year)) ? 366 : 365;

                break;
            default:
                return Functions::NAN();
        }

        return $daysPerYear;
    }
daysPerYear.

Returns the number of days in a specified year, as defined by the "basis" value

@param int $year The year against which we're testing
@param int $basis The type of day count:
0 or omitted US (NASD)    360
1                        Actual (365 or 366 in a leap year)
2                        360
3                        365
4                        European 360

@return int