Convert Atypical Date Format for Time Series in Python
Let pandas determine what datetime format you are using automatically. 

import pandas as pd
raw_data = pd.DataFrame(data={'BC_DT':['27-MAR-18','28-MAR-18','29-MAR-18']})
raw_data['BC_DT'] =  pd.to_datetime(raw_data['BC_DT'])
print(raw_data)



  BC_DT 0:   2018-03-27 1:  2018-03-28 2:  2018-03-29