YYYY vs yyyy

Foo.java

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

public class Foo {
  public static void main(String[] argv) {

    TimeZone utc = TimeZone.getTimeZone("UTC");

    SimpleDateFormat cy = new SimpleDateFormat("yyyy");
    cy.setTimeZone(utc);

    SimpleDateFormat wy = new SimpleDateFormat("YYYY");
    wy.setTimeZone(utc);

    Calendar calendar = new GregorianCalendar();
    calendar.setTimeZone(utc);
    calendar.set(2010, 0, 1);

    Date d = calendar.getTime();

    String cal  = cy.format(d);
    String week = wy.format(d);

    System.out.println(d + " Calendar year: " + cal + "; Week year: " + week);
  }
}

$ java Foo
Fri Jan 01 01:28:57 PST 2010 Calendar year: 2010; Week year: 2010

FWIW, POSIX date doesn't seem to have that problem. At least, on an ubuntu 14.04 system running in UTC timezone.

$ date -d '2010-01-01' -u +'%G-W%V-%u'
2009-W53-5

Also apparently fixed in newer versions of Java 7 than I have.