A DESCRIPTION OF THE PROBLEM :
Mon Sep 12 15:30:45 GMT 2005 roll(HOUR,24) get Mon Sep 12 16:30:45 GMT 2005.
I think the correct result should be Mon Sep 12 15:30:45 GMT 2005.


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Mon Sep 12 15:30:45 GMT 2005
Mon Sep 12 14:30:45 GMT 2005
Mon Sep 12 15:30:45 GMT 2005
Mon Sep 12 15:30:45 GMT 2005
ACTUAL -
Mon Sep 12 15:30:45 GMT 2005
Mon Sep 12 14:30:45 GMT 2005
Mon Sep 12 15:30:45 GMT 2005
Mon Sep 12 16:30:45 GMT 2005

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import java.util.GregorianCalendar;
import static java.util.Calendar.HOUR;
import java.util.Locale;
import java.util.TimeZone;

public class DateRollTest{
    public static void main(String[] args) {
        TimeZone.setDefault(TimeZone.getTimeZone("GMT"));
        GregorianCalendar cal = new GregorianCalendar(TimeZone.getTimeZone("GMT"), Locale.US);
        cal.clear();
        cal.set(2005, 8, 12, 15, 30, 45);
        System.out.println(cal.getTime());
        cal.roll(HOUR, 23);
        System.out.println(cal.getTime());


        cal.clear();
        cal.set(2005, 8, 12, 15, 30, 45);
        System.out.println(cal.getTime());
        cal.roll(HOUR, 24);
        System.out.println(cal.getTime());
    }

}
---------- END SOURCE ----------