python转化excel数字日期为标准日期操作

import pandas as pd
import datetime
data=pd.read_excel(r'xxxx.xlsx')
col=list(data.columns)#获取列名
print(col)
col_new=[]
def date(dates):#定义转化日期戳的函数,dates为日期戳
  delta=datetime.timedelta(days=dates)
  today=datetime.datetime.strptime('1899-12-30','%Y-%m-%d')+delta#将1899-12-30转化为可以计算的时间格式并加上要转化的日期戳
  return datetime.datetime.strftime(today,'%Y-%m-%d')#制定输出日期的格式
for x in range(len(col[2:9])):#将excel的时间戳循环替换
  col_date=date(col[2:9][x])
  col_new.append(col_date)
col[2:9]=col_new
data.columns=col

import openpyxl
import datetime
wb = openpyxl.Workbook()
ws = wb.active
ws.title
ws['A1'] = 520
ws.append([1,2,3])
ws['A3'] = datetime.datetime.now()
wb.save('time.xlsx')