Python: Am trying to get time difference between y and x, it gives me -ve value in milliseconds. from datetime import datetime x = 2018-01-28 08:58:10.83 y = 2018-01-28 08:58:10.144 x_time = datetime.strptime(x, '%Y-%m-%d %H:%M:%S.%f') # 2018-01-28 08:58:10.830000 y_time = datetime.strptime(y, '%Y-%m-%d %H:%M:%S.%f') # 2018-01-28 08:58:10.144000 diff = y_time - x_time duration_milliseconds = round(diff.total_seconds() * 1000) print(duration_milliseconds) # -686 

Result : -686

Expected: 61