Python xlsx转csv，不将日期更改为整数

import openpyxl
import csv

def xlsx_to_csv(filename):
    wb = openpyxl.load_workbook(filename)
    sheet = wb.active

    with open('output.csv', 'w', newline='') as csvfile:
        writer = csv.writer(csvfile)
        for row in sheet.iter_rows():
            csv_row = []
            for cell in row:
                if cell.value is None:
                    csv_row.append('')
                elif isinstance(cell.value, (int, float)):
                    csv_row.append(cell.value)
                else:
                    csv_row.append(str(cell.value))
            writer.writerow(csv_row)

xlsx_to_csv('input.xlsx')