python 时间格式转换

from datetime import timedelta

num = pd.read_excel('结果.xlsx', sheet_name='初日')
num = np.array(num)
date_num = np.zeros([60, 346])
date_pd = pd.Dataframe(np.zeros([60, 345]))

for row in range(3, 63):
    for col in range(1, np.size(num, 1)):
        t0 = datetime.date(2021, 1, 1)
        if num[row, col] != 0:
            days = t0 + timedelta(num[row, col] - 1)
            date_num[row - 3, col] = int(days.strftime('%m%d'))
            strnum = str(days.strftime('%m%d'))
            date_pd[col-1][row - 3]=(strnum[0:2]+'月'+strnum[2:5]+'日')
        else:
            date_num[row - 3, col] = np.nan
            date_pd[col-1][row - 3]= "--"
df = pd.Dataframe(date_pd)
df.to_clipboard(index=False, header=False)