code: public static String datetime(long millis) {
  		if (sFormat == null) {
  			sFormat = FastDateFormat.getInstance("yyyy-MM-dd HH:mm:ss", TimeZone.getTimeZone("UTC"),
  					US);
  		}
  		return sFormat.format(millis);
  	}
docs: Get UTC date and time for the milliseconds since the epoch, in the format
  {@code YYYY-MM-DD hh:mm:ss}.