title: Behind The Scenes: Core Data dates stored with 31 year offset?
body: <p>I know, "no user-serviceable parts inside" ... but I'm curious:</p>
  
  <p>In a Core Data sqlite3 DB, it seems I can get at the date within a ZDATE like so:</p>
  
  <pre><code>sqlite&gt; select datetime(ZDATE,'unixepoch','31 years','localtime') from ZMYCLASS;
  2003-12-11 19:00:00
  2009-12-31 19:00:00
  2009-01-24 19:00:00
  2011-01-01 19:00:00
  2009-10-03 20:00:00
  ...
  </code></pre>
  
  <p>Unix Epoch I get, but why 31 years?</p>