public String getGPSDateTime(){
        final String[] dt = {"", ""};
        final GpsDirectory gps = md.getDirectory(GpsDirectory.class);
        
        if (gps == null) {
            return null;
        }
        for (final Tag t:gps.getTags()) {
            if (t.getTagName().equals("GPS Date Stamp")) {
                dt[0] = t.getDescription();
            }
            if (t.getTagName().equals("GPS Time-Stamp")) {
                dt[1] = t.getDescription();
            }
        }
        if (dt[0].isEmpty()) {
            return null;
        }
        final Matcher m = pat.matcher(dt[1]);
        // TODO: fix this in metadata extractor code
        if (m.find()) {
            dt[1] = m.group(1) + m.group(2) + " " + m.group(3) + "0";
        }
        dt[0] = dt[0].replace(":", "/");
        return dt[0] + " " + dt[1];
    }