df_EVENT5_5['dtin'] = pd.to_datetime(df_EVENT5_5['dtin'])
df_EVENT5_5['age'] = df_EVENT5_5['dtin'].apply(dt.datetime.date) - df_EVENT5_5['dtbuilt'].apply(dt.datetime.date)

id  age
1   6252 days, 0:00:00
2   1800 days, 0:00:00
3   5873 days, 0:00:00

id  age
1   6252
2   1800
3   5873

df_EVENT5_5['age_no_days'] = df_EVENT5_5['age'].dt.total_seconds()/ (24 * 60 * 60)