Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Calculation/DateTime.php
private static function getTimeValue($timeValue)
    {
        $saveReturnDateType = Functions::getReturnDateType();
        Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
        $timeValue = self::TIMEVALUE($timeValue);
        Functions::setReturnDateType($saveReturnDateType);

        return $timeValue;
    }
private static function getTimeValue($timeValue)
    {
        $saveReturnDateType = Functions::getReturnDateType();
        Functions::setReturnDateType(Functions::RETURNDATE_EXCEL);
        $timeValue = self::TIMEVALUE($timeValue);
        Functions::setReturnDateType($saveReturnDateType);

        return $timeValue;
    }
getTimeValue.

@param string $timeValue

@return mixed Excel date/time serial value, or string if error