HttpURLConnection hc = (HttpURLConnection) new URL(tldurl).openConnection(); if (modTime > 0) { SimpleDateFormat sdf = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss z");//Sun, 06 Nov 1994 08:49:37 GMT String since = sdf.format(new Date(modTime)); hc.addRequestProperty("If-Modified-Since", since); }