Convert date to GMT

import java.util.Calendar;
import java.util.TimeZone;

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

  }
  public Calendar toGMT() {
    return toTimeZone("GMT");
}
  public Calendar toTimeZone(String tz) {
    Calendar cal = Calendar.getInstance();
    cal.setTimeZone(TimeZone.getTimeZone(tz));
    return cal;
  }
}