ValueError: time data '2021-01-01 00:00:00' does not match format 'yyyy-MM-dd HH:mm:ss code example

Example: time data '23-05-2017 08:00:00' does not match format 'dd-MM-yyyy HH:mm:ss'

>>> from datetime import datetime
>>> datetime.strptime('07/28/2014 18:54:55.099000', '%m/%d/%Y %H:%M:%S.%f')
datetime.datetime(2014, 7, 28, 18, 54, 55, 99000)