public class Date {
  private int day;
  private int month;
  private int year;

  // Constructor 
  public Date(int m, int d, int y) {
    day = d;
    month = m;
    year = y;
  }

  // Returns the Date obtained by adding nDays to the receiving
  // Date object.
  public Date add(int nDays) {
    Date d1 = new Date(month,day,year);
    for (int i=0; i < nDays; i++)
      d1 = d1.nextDay();
    return d1;
  }

  // Returns the Date obtained by subtracting nDays from the receiving
  // Date object.
  public Date sub(int nDays) {
    Date d1 = new Date(month,day,year);
    for (int i=0; i < nDays; i++)
      d1 = d1.previousDay();
    return d1;
  }

  // Returns the number of days between d and the receiving Date object
  public int daysBetween(Date d) {
    Date eDate, lDate;

    if (this.equals(d))
      return 0;
    else {
      if (this.before(d)) { eDate = this; lDate = d; }
      else { eDate = d; lDate = this; }
      int count = 0;
      for (Date d1 = eDate; eDate.before(lDate); eDate = eDate.nextDay())
        count++;
      return count;
    } 
  }

  // Returns true if the receiving Date object is after Date d.
  public boolean after(Date d) {
    if (this.year > d.year)
      return true;
    else if (this.year < d.year)
      return false;
    else if (this.month > d.month)
      return true;
    else if (this.month < d.month)
      return false;
    else if (this.day > d.day)
      return true;
    else if (this.day < d.day)
      return false;
    else
      return false;
  }

  // Returns true if the receiving Date object is same as Date d.
  public boolean equals(Date d) {
    return ((this.year == d.year) &&
            (this.month == d.month) &&
            (this.day == d.day));
  }

  // Returns true if the receiving Date object is before Date d.
  public boolean before(Date d) {
    return !(this.equals(d) || this.after(d));
  }

  // Returns the Date object corresponding to the previous day for the
  // receiving Data object.
  public Date previousDay() {
    int d=0,m=0,y=0;
    Date yesterday=new Date(m,d,y);

    if (day > 1) {
      d = day - 1;
      m = month;
      y = year;
      yesterday = new Date(m,d,y);
      return yesterday;
    }
    else {
      switch (month) {    
        case 2: case 4: case 6: case 8: case 9: case 11: 
          d = 31; m = month - 1; y = year; break;

        case 5: case 7: case 10: case 12: 
          d = 30; m = month - 1; y = year; break;

        case 1:
          d = 31; m = 12; y = year-1; break;

        case 3:
          if (!leapYear(year)) {
            d = 28; m = 2; y = year; 
          }
          else {
            d = 29; m = 2; y = year; 
          }
          break;
      }
      yesterday = new Date(m,d,y);
      return yesterday;
    }
  }

  // Returns the Date object corresponding to the first day of the
  // previous month for the receiving Data object.
  public Date firstOfPreviousMonth() {
    Date d;

    if (month > 1) 
      d = new Date(month-1,1,year);
    else
      d = new Date(12,1,year-1);

    return d;
  }

  // Returns the Date object corresponding to the next day for the
  // receiving Data object.
  public Date nextDay() {
    int d=0,m=0,y=0;
    Date tomorrow=new Date(m,d,y);

    switch (month) {    
      case 1: case 3: case 5: case 7: case 8: case 10: 
        if (day < 31) { d = day + 1; m = month; y = year; }
        else { d = 1; m = month + 1; y = year; }
        break;

      case 4: case 6: case 9: case 11: 
        if (day < 30) { d = day + 1; m = month; y = year; }
        else { d = 1; m = month + 1; y = year; }
        break;

      case 12:
        if (day < 31) { d = day + 1; m = month; y = year; }
        else { d = 1; m = 1; y = year+1; }
        break;

      case 2:
        if (((day == 28) && !leapYear(year)) ||
            ((day == 29) && leapYear(year)) ) {
          d = 1; m = month+1; y = year; }
        else { d = day + 1; m = month; y = year; }
        break; 
    }
    tomorrow = new Date(m,d,y);
    return tomorrow;
  }

  // Returns the Date object corresponding to the first day of the
  // next month for the receiving Data object.
  public Date firstOfNextMonth() {
    Date d;

    if (month < 12) 
      d = new Date(month+1,1,year);
    else
      d = new Date(1,1,year+1);

    return d;
  }

  // Pretty print method
  public String toString() {
    String sMonths = 
       "01January:02February:03March:04April:05May:06June:" +
       "07July:08August:09September:10October:11November:12December:";
    String m;
    if (month < 10) m = "0"+month; else m = ""+month;
    int i = sMonths.indexOf(m);
    int j = sMonths.indexOf(":",i+1);
    String sMonth = sMonths.substring(i+2,j);
    return day + " " + sMonth + ", " + year; 
  }

  private static boolean leapYear(int year) {
    return  ((year%4 == 0) && !(year%100 == 0 && year%400 != 0));
  }

}