Bug in JDK1.4.x Calendar ???

Question

Hi,
I have the below function for calculating the days between two dates. Its working fine in JDK 1.3.x version resulting correct values and in JDK1.4.2_04 version its giving wrong values. For any dates that overlap with Daylight savings Start and End dates the results are off by 1 day.
Ex:
04/02/2005 and 04/04/2005 (MM/DD/YYYY) .The result shd be 2 but its giving as 1. In JDK 1.3.x version it is giving 2.
Its a production issues with high priority need help .....
Thanks you all,
public static long diffTwoDays(Timestamp tsStart, Timestamp tsEnd) throws Exception
String methodName = "diffTwoDays";
String strStartDate=null;
String strEndDate=null;
long lStart=0;
long lEnd=0;
long numDays=0;
try
strStartDate=tsStart.toString();
Calendar cal1 = Calendar.getInstance();
cal1.set(Calendar.YEAR,Integer.parseInt(strStartDate.substring(0,4)));
cal1.set(Calendar.MONTH,(Integer.parseInt(strStartDate.substring(5,7))-1));
cal1.set(Calendar.DAY_OF_MONTH,Integer.parseInt(strStartDate.substring(8,10)));
cal1.set(Calendar.HOUR_OF_DAY,0);
cal1.set(Calendar.MINUTE,0);
cal1.set(Calendar.SECOND,0);
cal1.set(Calendar.MILLISECOND,0);
cal1.set(Calendar.ZONE_OFFSET,0);
lStart=(cal1.getTime().getTime());
strEndDate=tsEnd.toString();
Calendar cal2 = Calendar.getInstance();
cal2.set(Calendar.YEAR,Integer.parseInt(strEndDate.substring(0,4)));
cal2.set(Calendar.MONTH,(Integer.parseInt(strEndDate.substring(5,7))-1)) ;
cal2.set(Calendar.DAY_OF_MONTH,Integer.parseInt(strEndDate.substring(8,10)));
cal2.set(Calendar.HOUR_OF_DAY,0);
cal2.set(Calendar.MINUTE,0);
cal2.set(Calendar.SECOND,0);
cal2.set(Calendar.MILLISECOND,0);
cal2.set(Calendar.ZONE_OFFSET,0);
lEnd=(cal2.getTime().getTime());
numDays=(lEnd-lStart)/(1000*60*60*24);
} catch (Exception e)
LogTracer.writeTracerLog(className,methodName,e);
throw new Exception(e.getMessage());
return numDays;
}

Answer 1

If I were you, I'd make diffTwoDays a little less error-prone. Setting fields in the Calendar object can have bad consequences if you don't know what you're doing. As warnerja said, the TIMEZONE_OFFSET should not be explicitly set, especially not after you've set everything else. Also, don't assume the format of Timestamp.toString(); and don't try to calculate things you don't (need to) understand. There's probably a more efficient way of doing this....
public static long diffTwoDays(Timestamp tsStart, Timestamp tsEnd)
     Calendar s = Calendar.getInstance();
     s.setTimeInMillis(tsStart.getTime());
     Calendar e = Calendar.getInstance();
     e.setTimeInMillis(tsEnd.getTime());
     long numDays = 0;
     int i;
     while (e.get(Calendar.YEAR) > s.get(Calendar.YEAR))
          i = e.get(Calendar.DAY_OF_YEAR);
          numDays += i;
          e.add(Calendar.DAY_OF_YEAR, -i);
     while (e.get(Calendar.MONTH) > s.get(Calendar.MONTH))
          i = e.get(Calendar.DAY_OF_MONTH);
          numDays += i;
          e.add(Calendar.DAY_OF_MONTH, -i);
     return numDays + e.get(Calendar.DATE) - s.get(Calendar.DATE);
}