title: How to set the modifiedDate on a google drive file in iOS AND prevent duplicate file names
body: <p>I found the way in iOS (not obvious to me) to insert a file into a google drive folder using the standard queryForFilesInsertWithObject with uploadParameters and setting the folder id in a GTLDriveParentReference object, adding that object to an array, and assigning that array to the uploaded file's "parents" property.  What I haven't yet figured out is how to overwrite any existing google drive file with a newer version without creating a duplicate.  I would also like to stamp the new uploaded google drive file with the same date-time stamp as my local device file.  When I try to use the file/update method and set the file.modifiedDate and query.setModifiedDate=YES, I always get a 400 Bad Request.</p>
  
  <p>I can use patch to change the title just fine, but I can't set the modifiedDate using the api. I was able to change the modifiedDate using Google's Try it! APIs Explorer, so Google's servers are working fine. Here is the code that fails:</p>
  
  <pre><code>GTLDriveFile *file = [GTLDriveFile object];
  NSString *fId = insertedFile.identifier;
  file.title = @"Tony.jpg";
  file.modifiedDate = myNewGoogleDate; // "2012-12-31T08:00:00+00:00"
  
  GTLQueryDrive *qu = [GTLQueryDrive queryForFilesPatchWithObject:file fileId:fId];
  qu.setModifiedDate = YES;
  
  [service executeQuery:qu completionHandler:^(GTLServiceTicket *ticket,...
  </code></pre>
  
  <p>Take out the two lines with modifiedDate and the google-drive file title changes just fine.  I traced into the api call to executeQuery and found that the following results as "DataToPost".</p>
  
  <pre><code>{"method":"drive.files.patch","id":"gtl_7","jsonrpc":"2.0",
  "params": {"setModifiedDate":true,"resource":
  {"modifiedDate":"2012-12-31T08:00:00+00:00",
  "title":"Tony.jpg"},"fileId":"0BxRlXPR_hfR9OEJSdDdyQjkyaE0"},"apiVersion":"v2"}
  </code></pre>
  
  <p>Does anyone see "Bad Request" in this post?  The error returned from the executeQuery is:</p>
  
  <pre><code>Error Domain=com.google.GTLJSONRPCErrorDomain Code=400 "The operation couldn’t be
  completed. (Bad Request)" UserInfo=0x80724b0 {error=Bad Request,
  GTLStructuredError=GTLErrorObject 0x806a7a0: {message:"Bad Request" code:400 data:[1]},
  NSLocalizedFailureReason=(Bad Request)}
  </code></pre>
  
  <p>Does anyone have some code to set the modifiedDate that works?</p>