As mentioned by sibling comments, it's because you're not specifying a year. If you change the day to the 28th you'll see that it defaults to the year 1900:

  >>> datetime.strptime('Feb 28 04:55:03.687', '%b %d %H:%M:%S.%f')
  datetime.datetime(1900, 2, 28, 4, 55, 3, 687000)

  >>> datetime.strptime('Feb 28 13:37:06.942', '%b %d %H:%M:%S.%f') 
  datetime.datetime(1900, 2, 28, 13, 37, 6, 942000)