Reasons for preferring an immutable representation:

• the mutable Date class requires more care than a long integer
• the Date class itself has many deprecations, replaced by methods in DateFormat, Calendar, and GregorianCalendar
• you may use long as a simple, locale-independent representation of a date, and use the date-related classes to provide a particular view of that date

Here, a simple long is used to encapsulate a date:

package myapp.business;

import java.util.*;

public final class Movie {

  public Movie(String aTitle, long aReleaseDate){
    fTitle = aTitle;
    fReleaseDate = aReleaseDate;
  }

  public Movie(String aTitle, Date aReleaseDate){
    this(aTitle, aReleaseDate.getTime());
  }

  /**
  * The caller of this method decides on the
  * presentation format of the date, if necessary.
  */
  public long getReleaseDate(){
    return fReleaseDate;
  }

  public String getTitle() {
    return fTitle;
  }

  //..other methods elided

  // PRIVATE 
  private String fTitle;
  private long fReleaseDate;
}