title: Save date time in filename with valid chars
body: <p>To keep track of my when my files were backed up I want to have the filename of the backups as the datetime of when they were backed up. This will eventually be sorted and retrieved and sorted using python to allow me to get the most recent file based on the datetime filename.</p>
  
  <p>The problem is, the automatic format of date time cant be saved like this:</p>
  
  <p>2007-12-31 22:29:59</p>
  
  <p>It can for example be saved like this:</p>
  
  <p>2007-12-31 22-29-59</p>
  
  <p>What is the best way to format the datetime so that I can easily sort by datetime on the name, and for bonus points, what is the python to show the datetime in that way.</p>