How to change datetime_index in Rodeo Python dataframe to datetime?

Question

in Rodeo I created a dataframe with column 'Date' as a range of Date by inputing:

temp_df = pd.DataFrame({
    'Date': pd.date_range('2017-01-01',periods=100,freq='D'),
    'Value': np.random.normal(10,5,size=100).tolist()
})

However, when I click on the dataframe, it shows

Date 1483228800000 1483315200000 1483401600000 1483488000000 ...

in the 'Date' column. Yet, the datetime format works properly when I try:

>>> temp_df.Date.head()
0   2017-01-01
1   2017-01-02
2   2017-01-03
3   2017-01-04
4   2017-01-05

May I know what am I missing in my code? Thanks a lot.