Python, 시계열 데이터 컬럼 만들어주기

test_data_1 = pd.DataFrame({'집계일자' : ['20210919', '20210919','20210919','20210919','20210919','20210919'], \
                            '집계시' : ['8', '9', '10', '11', '12', '13']})

display(test_data_1, "위의 df가 아래처럼 변함")

all_2017_copy1 = test_data_1.copy()

for i in range(all_2017_copy1['집계일자'].shape[0]):
    result1 = str(all_2017_copy1['집계일자'][i])[:4]
    result2 = result1 + '-'
    result3 = result2 + str(all_2017_copy1['집계일자'][i])[4:6]
    result4 = result3 + '-'
    result5 = result4 + str(all_2017_copy1['집계일자'][i])[-2:]
    all_2017_copy1.loc[i, '집계일자'] = result5
a = []
for n in range(all_2017_copy1['집계시'].shape[0]):
    
    result1 = int(all_2017_copy1['집계시'][n])
    if result1 < 10:
        result2 = ' 0' + str(result1) + ':00:00'
    else:
        result2 = ' ' + str(result1) + ':00:00'
    alll = all_2017_copy1.loc[n, '집계일자'] + result2
    all_2017_copy1.iloc[n, 0] = alll

all_2017_copy1['집계일자'] = pd.to_datetime(all_2017_copy1['집계일자'])

test_data_finish = all_2017_copy1.copy()

display(test_data_finish) #  all_2017_copy1.info())
# all_2017_copy1.to_csv('all_2021_date.csv')