Did I find a java.util.Calendar bug?

I have the following test:

import static org.junit.Assert.assertEquals;

import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.TimeZone;

import org.junit.Test;
public class CalendarBug {
    private static final TimeZone UTC_ZONE = TimeZone.getTimeZone("UTC");// +0 hours
    private static final TimeZone IST_ZONE = TimeZone.getTimeZone("IST");// +5 hours 30 minutes

    @Test
    public void calendarBug() {
        Calendar utcCalendar = Calendar.getInstance(UTC_ZONE);
        utcCalendar.set(Calendar.YEAR, 2015);
        utcCalendar.set(Calendar.MONTH, 3);
        utcCalendar.set(Calendar.DAY_OF_MONTH, 12);
        utcCalendar.set(Calendar.HOUR_OF_DAY, 10);
        utcCalendar.set(Calendar.MINUTE, 0);
        utcCalendar.set(Calendar.SECOND, 0);
        SimpleDateFormat utcFormatter = new SimpleDateFormat( "yyyy-MM-dd HH:mm:ss Z" );
        utcFormatter.setTimeZone(UTC_ZONE);
        System.out.println( "If I have this line commented out, the test fails: " + utcFormatter.format(utcCalendar.getTime()));
        Calendar istCalendar = (Calendar) utcCalendar.clone();
        assertEquals(UTC_ZONE, istCalendar.getTimeZone());
        istCalendar.setTimeZone(IST_ZONE);
        assertEquals(istCalendar.getTimeInMillis(), utcCalendar.getTimeInMillis());
    }
}

If you run the test, it works. However if you comment out the System.out.println line with the formatter inside, it fails:

java.lang.AssertionError: expected:<1428813000979> but was:<1428832800979>
    at org.junit.Assert.fail(Assert.java:93)
    at org.junit.Assert.failNotEquals(Assert.java:647)
    at org.junit.Assert.assertEquals(Assert.java:128)
    at org.junit.Assert.assertEquals(Assert.java:472)
    at org.junit.Assert.assertEquals(Assert.java:456)
    at xxx.yyy.CalendarBug.calendarBug(CalendarBug.java:29)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

It seems that the formatter changes the internal state of the utcCalendar and it causes the test to pass.

Did I misuse anything here? Is there an open bug in JDK for this?

Java version:

liptak@XXXXXX:~$ java -version
java version "1.7.0_60"
Java(TM) SE Runtime Environment (build 1.7.0_60-b19)
Java HotSpot(TM) 64-Bit Server VM (build 24.60-b09, mixed mode)