rent_date_raw = pd.Series(1, rent['RENT_DATE'])
return_date_raw = pd.Series(1, rent['RETURN_DATE'])
rent_date = pd.Series([pd.to_datetime(date)
                       for date in rent_date_raw])
daily_rent_ts = rent_date.resample('D', how='count')
monthly_rent_ts = rent_date.resample('M', how='count')