Roll java.util.Date back and forth

import java.util.GregorianCalendar;

public class Main {
  /**
   * Roll the java.util.Date forward or backward.
   * @param startDate - The start date
   * @period Calendar.YEAR etc
   * @param amount - Negative to roll backwards.
   */
   public static java.util.Date rollDateTime( java.util.Date startDate, int period, int amount )
   {
       GregorianCalendar gc = new GregorianCalendar();
       gc.setTime(startDate);
       gc.add(period, amount);
       return new java.util.Date(gc.getTime().getTime());
   }
}