In SQL How to convert time intoUNIX_timestamp : In hive there is some data I have. Now I want to convert the start_timestamp into unix_timestamp in second. How to do? Because the start_timestamp has two format.

start_timestamp
First format : 2018-03-22 02:54:35 , Second Format: May 15 2018  5:15PM

Any help? Appreciate your help. Thanks