Android : Google Drive SDK getModifiedDate() different from setModifiedDate()

I'm running into an issue with the 'setModifiedDate()' method of the 'Google Drive Web APIs', and I don't know if it is by design, or a bug.

When updating modified date using the following construct:

  DateTime md = DateTime.parseRfc3339("2014-11-02T12:09:58.000-07:00");
  File body = new File().setModifiedDate(md);
  service.files().patch(id, body).setSetModifiedDate(true).execute();

the date/time updates correctly. Notice that input DateTime variable md can be shown as

2014-11-02T12:09:58.000-07:00, and 
md.getTimeZoneShift() reports -420 minutes

When later reading the file's modified date using for instance this construct:

FileList gLst = service.files().list().execute();
for (File gFl : gLst.getItems()) 
  md = gFl.getModifiedDate();

the DateTime 'md' variable holds the correct GMT time, but the time shift (UTC offset) info is lost. the time would be reported as

2014-11-02T19:09:58.000Z and 
md.getTimeZoneShift() reports 0 minutes

which certainly IS CORRECT ZULU (GMT) time for the file, but the fact that it was modified from my timezone (GMT-07:00) is lost. I would expect to get the same DateTime format, i.e.

2014-11-02T12:09:58.000-07:00 
and md.getTimeZoneShift() reports -420 minutes

as I patched.

Is it the correct behavior, or am I missing something?