title: How might one implement FileTimeToSystemTime?
body: <p>I'm writing a simple wrapper around the Win32 FILETIME structure. <code>boost::datetime</code> has most of what I want, except I need whatever date type I end up using to interpolate with Windows APIs without issues.</p>
  
  <p>To that end, I've decided to write my own things for doing this -- most of the operations aren't all that complicated. I'm implementing the TimeSpan - like type at this point, but I'm unsure how I'd implement FileTimeToSystemTime. I could just use the system's built-in FileTimeToSystemTime function, except FileTimeToSystemTime cannot handle negative dates -- I need to be able to represent something like "-12 seconds".</p>
  
  <p>How should something like this be implemented?</p>
  
  <p>Billy3</p>