Calendar.add for Central African Timezone (GMT +2)

Question

Hi all,
I am trying to add x days to 1900-01-01 06:00 at the Central African Timezone (GMT +2). However, the result from simple Calendar.add(Calender.DATE, numDays) is giving me 4 min and 12 seconds less. This only happens when the final date pass March 1, 1903 (which is the only DST day of Central African).
ie:
origDate = 1900-01-01 06:00 CAT
numDaysToAdd = 1154
resultDate = 1903-03-01 05:55:48 CAT (instead of 06:00)
I searched around the bug database and someone suggests to always use GMT to do calendar calculation. However, with that, I will get 2 extra hours.
ie:
origDate = 1900-01-01 06:00 CAT
numDaysToAdd = 1154
resultDate = 1903-03-01 08:00:00 CAT (instead of 06:00)
Any idea on how to work this out?
Here is the test code:
import java.util.*;
import java.math.*;
public class Test2
public static void main(String[] args) {
TimeZone.setDefault(TimeZone.getTimeZone("Africa/Harare"));
// Create a date set the Time to 1900/01/01 06:00 AM
Calendar now = Calendar.getInstance();
          now.set(1900, 0, 1, 6, 0, 0);
          Date d = new Date(now.getTimeInMillis());
          System.out.println(d.toString());          
     System.out.println();
          // try to add 1154 days to d with GMT timezone
          Date d2 = addDaysWithGMT(d, 1154);
          System.out.println("Extra two hours: " + d2.toString());
          System.out.println();
          // try to add 1154 days to d with original timezone
          d2 = addDays(d, 1154);
          System.out.println("Missing 4 minutes and 12 seconds: " + d2.toString());
     public static Date addDaysWithGMT(Date d, int days) {
Calendar now=Calendar.getInstance();
          now.setTimeZone(TimeZone.getTimeZone("GMT"));
          now.set(d.getYear() + 1900, d.getMonth(), d.getDate(), d.getHours(), d.getMinutes(), d.getSeconds());
          System.out.println("after set: " + now.getTime());
          now.add(Calendar.DATE,days);
          System.out.println("after add: " + now.getTime());
          now.setTimeZone(TimeZone.getDefault());
          return new Date(now.getTimeInMillis());
     public static Date addDays(Date d, int days) {
Calendar now=Calendar.getInstance();
          now.set(d.getYear() + 1900, d.getMonth(), d.getDate(), d.getHours(), d.getMinutes(), d.getSeconds());
          System.out.println("after set: " + now.getTime());
          now.add(Calendar.DATE,days);
          System.out.println("after add: " + now.getTime());
          return new Date(now.getTimeInMillis());
Any help would be appreciated.
Thanks,
Winnie

Answer 1

Not going to read all that, especially with the unformatted code. However, a couple of things leap out at me.
* 1903
* 4 min., 12 sec.
As a rough guess, this sounds like an accumulation of leap seconds.
As a second out-of-my-butt guess--this TZ might be one of the less common/"popular"/well-known ones, so it's possible that it has various adjustments to its rules over the years. Note that I don't really know what I'm talking about here--just venting a vague gut feeling.