function [ n_data, d, m, y ] = easter_gregorian_values ( n_data )

%*****************************************************************************80
%
%% easter_gregorian_values() returns some Easter dates in Gregorian calendar.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    03 January 2018
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    integer N_DATA.  The user sets N_DATA to 0 before the first call.  
%    Thereafter, it should simply be the value returned by the previous call.
%
%  Output:
%
%    integer N_DATA.  On each call, the routine increments N_DATA by 1, and
%    returns the corresponding data; when there is no more data, the
%    output value of N_DATA will be 0 again.
%
%    integer D, M, Y, a date for Easter.
%
%    integer DATE_NUM, the MATLAB datenum for the date.
%
  n_max = 10;

  d_vec = [   30,   12,    4,   23,   15,   31,   20,   11,   27,   16 ];
  m_vec = [    3,    4,    4,    4,    4,    3,    4,    4,    3,    4 ];
  y_vec = [ 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006 ];

  if ( n_data < 0 )
    n_data = 0;
  end

  n_data = n_data + 1;

  if ( n_max < n_data )
    n_data = 0;
    d = 0;
    m = 0;
    y = 0;
  else
    d = d_vec(n_data);
    m = m_vec(n_data);
    y = y_vec(n_data);
  end

  return
end
