grib/src/main/java/ucar/nc2/grib/grib2/Grib2Pds.java
protected CalendarDate calcTime(int startIndex) {

    int year = GribNumbers.int2(getOctet(startIndex++), getOctet(startIndex++));
    int month = getOctet(startIndex++);
    int day = getOctet(startIndex++);
    int hour = getOctet(startIndex++);
    int minute = getOctet(startIndex++);
    int second = getOctet(startIndex++);

    if ((year == 0) && (month == 0) && (day == 0) && (hour == 0) && (minute == 0) && (second == 0))
      return CalendarDate.UNKNOWN;

   // href.t00z.prob.f36.grib2
     if (hour > 23) {
       day += (hour/24);
       hour = hour % 24;
     }

    return CalendarDate.of(null, year, month, day, hour, minute, second);
  }
protected CalendarDate calcTime(int startIndex) {

    int year = GribNumbers.int2(getOctet(startIndex++), getOctet(startIndex++));
    int month = getOctet(startIndex++);
    int day = getOctet(startIndex++);
    int hour = getOctet(startIndex++);
    int minute = getOctet(startIndex++);
    int second = getOctet(startIndex++);

    if ((year == 0) && (month == 0) && (day == 0) && (hour == 0) && (minute == 0) && (second == 0))
      return CalendarDate.UNKNOWN;

   // href.t00z.prob.f36.grib2
     if (hour > 23) {
       day += (hour/24);
       hour = hour % 24;
     }

    return CalendarDate.of(null, year, month, day, hour, minute, second);
  }
protected CalendarDate calcTime ( int startIndex ) { int year = GribNumbers . int2 ( getOctet ( startIndex ++ ) , getOctet ( startIndex ++ ) ) ; int month = getOctet ( startIndex ++ ) ; int day = getOctet ( startIndex ++ ) ; int hour = getOctet ( startIndex ++ ) ; int minute = getOctet ( startIndex ++ ) ; int second = getOctet ( startIndex ++ ) ; if ( ( year == 0 ) && ( month == 0 ) && ( day == 0 ) && ( hour == 0 ) && ( minute == 0 ) && ( second == 0 ) ) return CalendarDate . UNKNOWN ; // href.t00z.prob.f36.grib2
 if ( hour > 23 ) { day += ( hour / 24 ) ; hour = hour % 24 ; } return CalendarDate . of ( null , year , month , day , hour , minute , second ) ; }
null means use refTime
null means use refTime