import xlwt
import datetime


date=datetime.datetime(2021,7,1)

workbook = xlwt.Workbook()
worksheet = workbook.add_sheet('MySheet')

# 设置样式
style = xlwt.XFStyle()
style.num_format_str = 'YYYY-MM-DD'

# 写入数据，注意写入的是datetime对象类型
worksheet.write(0, 0, date, style)
workbook.save('test.xls')