title: Replacing time stamp in the Python logger
body: <p>I use the Python 2.7 standard <code>logging</code> module to do the logging for our system. Occasionally, we run a simulation of past events, and it would really be useful if instead of using the system time in <code>datetime.now()</code> I would be able to use my own custom system time.</p>
  
  <p>I know there is a way to use <code>Formatter</code> to alter the time string format, but can I actually alter the content of the logged time string as well?</p>
  
  <p>Thank you very much</p>