Getting difference between GMT time and Local time

Question

Folks,
I am trying to get difference between gmt time and local time for Korea time zone.
which should be 9 hours.
Instead of 9, I am getting 15 hours diff.
What am I doing wrong?
Here's what I did to test it:
First I set the system (Windows XP) time zone to Soul (Korea GMT+9hours) time zone.
Then I ran the following program, and I got 15 hour diff, not 9.
Thank you in advance!
import java.util.*;
public class Using_GregorianCalendar
     public static void main(String args[])
          Using_GregorianCalendar ugc = new Using_GregorianCalendar();
          ugc.getTimeDiff();
     public void getTimeDiff()
          Calendar cal = new GregorianCalendar(TimeZone.getTimeZone("GMT"));
          Calendar cal1 = new GregorianCalendar(cal.get(Calendar.YEAR),
                                       cal.get(Calendar.MONTH),
                                       cal.get(Calendar.DATE),
                                       cal.get(Calendar.HOUR_OF_DAY),
                                       cal.get(Calendar.MINUTE),
                                                  cal.get(Calendar.SECOND));
        int gmtHour          =  cal.get(Calendar.HOUR); //(Calendar.HOUR_OF_DAY);
        int gmtHourOfDay =  cal.get(Calendar.HOUR_OF_DAY);
        int gmtMonth        =  cal.get(Calendar.MONTH);
        int gmtYear          =  cal.get(Calendar.YEAR);
        int gmtMinute       =  cal.get(Calendar.MINUTE);
        int gmtSecond     =   cal.get(Calendar.SECOND);
        int gmtDate         = cal.get(Calendar.DATE);
        Calendar localCal  = Calendar.getInstance();
        int localHourOfDay = localCal.get(Calendar.HOUR_OF_DAY);
        int timeDiff = (localHourOfDay - gmtHourOfDay);
          //Korea time is GMT + 9 hours so I should get a difference of 9
          //why am I getting difference of 15?
             System.out.println("************** in getTimeDiff() **********************");
          System.out.println("gmtDate: "+gmtDate);
          System.out.println("gmtHour: "+gmtHour);
          System.out.println("gmtHourOfDay: "+gmtHourOfDay);
          System.out.println("localHourOfDay: "+localHourOfDay);
          System.out.println("timeDiff: "+timeDiff);
          System.out.println("**********************************************************");
     }//getTimeDiff()
}//class Using_GregorianCalendar
/*              here's the output of this program:
     ************** in getTimeInGMT() **********************
     gmtDate: 14
     gmtHour: 6
     gmtHourOfDay: 18
     localHourOfDay: 3
     timeDiff: -15
*/

Answer 1

DrClap wrote:
sabre150 wrote:
Nearly correct since the Daylight saving may or may not be in effect which does depend on the date...I would simplify that to this:
TimeZone korea = TimeZone.getTimeZone("Asia/Seoul");
long delta = korea.getOffset(new Date().getTime());
System.out.println(delta / (1000.0 * 60 * 60));That's assuming that the OP really meant UTC when he/she said "GMT". Most people don't realize there's a distinction and that Java's timezones are all based relative to UTC.I suspect you are right in assuming that the OP want UTC and not GMT. I figured it was better to illustrate that the method can be used for getting the time difference between any two TimeZones.