code: public static String gpsWeekTime2ISO8601( double gpsWeekTime ) {
          DateTime gps2unix = gpsWeekTime2DateTime(gpsWeekTime);
          return gps2unix.toString(ISO8601Formatter);
      }
docs: Convert GPS Time to ISO8601 time string.
  
  @param gpsWeekTime the gps time.
  @return the ISO8601 string of the gps time.