title: CoreData's `Date` type transforms `0000-01-01T00:00:00Z` to `nil`
body: <p>I'm new to iOS and CoreData, so I'm sorry if this is too basic.</p>
  
  <p>I'm trying to figure out why a valid-but-odd date of <code>0000-01-01T00:00:00Z</code> is being transformed to <code>nil</code>. eg:</p>
  
  <pre><code>calculatedAttrMapping.valueTransformer(@"0000-01-01T00:00:00Z"); // nil
  </code></pre>
  
  <p>This date should work, I think. It's valid by the RFC and ISO specs.</p>
  
  <pre><code>new Date("0000-01-01T00:00:00Z"); //Sat Jan 01 0 07:00:00 GMT+0700 (ICT)
  </code></pre>
  
  <p>(not that JS is relevant, but as a gut check...)</p>
  
  <p>I tried stepping into it in the debugger, but it goes to assembly before I see anything useful.</p>
  
  <p>Is this coming from the configuration in the <code>.xcdatamodeld</code> GUI?
  Is this intentional behavior? A limitation?</p>