cal.setTimeInMillis(gmt);
tree.addAttribute(_last_modified, String.format("%1$04d-%2$02d-%3$02dT%4$02d:%5$02d:%6$02dZ",
cal.get(Calendar.YEAR), cal.get(Calendar.MONTH)+1, cal.get(Calendar.DAY_OF_MONTH),
cal.get(Calendar.HOUR_OF_DAY), cal.get(Calendar.MINUTE), cal.get(Calendar.SECOND)));
tree.startContent();
tree.addEndElement();
} else {
tree.addStartElement(c_uri);
// Let's try HTTP