Converting Calendar Objects

Question

I seem to be having a problem converting between to timezones. What I want to do is convert an ISO DateTime string of the format YYYY-MM-DDThh:mm:ss in the local timezone to a similar format string in UTC. I have posted the code below. When I input a value of 2003-08-25:11:50:00, what I expect back is 2003-08-25T21:50:00 (based on my current timezone), but I actually get 2003-08-25T01:50:00     public String convertLocalISODatetoUTC(String isoDate) {
     // Parse the date to get the local Date
     Date date = parseDate(isoDate);
     String convertedDate = null;
     if (date != null) {
         // Break the string into tokens
         StringTokenizer st = new StringTokenizer(isoDate, "-T:");
         String yyyy  = st.nextToken();
         String mn    = st.nextToken();
         String dd    = st.nextToken();
         String hh    = st.nextToken();
         String mm    = st.nextToken();
         String ss    = st.nextToken();
         int millsecondsOfDay = (Integer.parseInt(hh)*3600 +
                        Integer.parseInt(mm)*60 +
                        Integer.parseInt(ss))*1000;
         GregorianCalendar cal = new  GregorianCalendar ( Integer.parseInt(yyyy),
                                        Integer.parseInt(mn) - 1,
                                        Integer.parseInt(dd),
                                        Integer.parseInt(hh),
                                        Integer.parseInt(mm),
                                        Integer.parseInt(ss) );
         System.out.println(cal.toString()); // debug line
         TimeZone tz = TimeZone.getDefault();
         int tzOffset = tz.getOffset (cal.get(Calendar.ERA),
                          cal.get(Calendar.YEAR),
                          cal.get(Calendar.MONTH),
                          cal.get(Calendar.DAY_OF_MONTH),
                          cal.get(Calendar.DAY_OF_WEEK),
                          millsecondsOfDay);
         cal.roll(Calendar.MILLISECOND,
              cal.get(Calendar.MILLISECOND) + tzOffset);
         cal.setTimeZone(TimeZone.getTimeZone("UTC"));
         System.out.println(cal.toString());             // debug-line
         System.out.println(cal.getTime().toString());   // debug-line
         SimpleDateFormat df = new SimpleDateFormat(isoFormat);
         convertedDate = df.format(cal.getTime());
         System.out.println("Convertd date = "+convertedDate);  // debug line
     return convertedDate;
    }

Answer 1

BTW, private final String isoFormat  = "yyyy-MM-dd'T'HH:mm:ss";