import datetime
workbook = xlwt.Workbook()
worksheet = workbook.add_sheet('Sheet1')
date_format = xlwt.XFStyle()
date_format.num_format_str = 'dd/mm/yyyy'
worksheet.write(0, 0, datetime.datetime.now(), date_format)
workbook.save('date_format.xls')
Writing xlwt dates with Excel 'date' format