Subset selected days data in Python

I have some time series data as:

import pandas as pd    
index = pd.date_range('06/01/2014',periods=24*30,freq='H')
df1 = pd.DataFrame(range(len(index)),index=index)

Now I want to subset data of below dates

selec_dates = ['2014-06-10','2014-06-15','2014-06-20']

I tried following statement but it is not working

sub_data = df1.loc[df1.index.isin(pd.to_datetime(selec_dates))]

Where am I doing wrong? Is there any other approach to subset selected days data?