function theEpicTime = EP_Time(y, m, d, h, mi, s)

% EP_Time -- Epic-time from Matlab date.
%  EP_Time(theDate) returns the epic-time [time time2]
%   that corresponds to theDate, a Matlab date-string,
%   date-number, or date-vector [y m d] or [y m d h mi s].
%   See the Matlab "datestr()", "datenum()", and "datevec()"
%   functions for syntax and restrictions.
%  EP_Time(y, m, d) and EP_Time(y, m, d, h, mi, s) provide
%   alternatives for date-vector input.
%  EP_Time('demo') demonstrates itself.
%  EP_Time (no argument) shows "help" and demonstrates itself.
 
% Copyright (C) 1997 Dr. Charles R. Denham, ZYDECO.
%  All Rights Reserved.
%   Disclosure without explicit written consent from the
%    copyright owner does not constitute publication.
 
% Version of 01-Jul-1997 15:54:18.

% Note: May 23, 1968 = Julian Day 2,440,000.

if nargin < 1, help(mfilename), y = 'demo'; end

if strcmp(y, 'demo')
   y = '23-May-1968';
   if exist('begets')
      begets('EP_Time', 1, y, ep_time(y))
     else
      disp([' ## EP_Time(''' y ''') ==> ' ep_time(y)])
   end
   return
end

switch nargin
case 1
   if isstr(y) | length(y) == 1
      theDate = datenum(y);
     elseif length(y) == 3
      d = y(3); m = y(2); y = y(1);
      theDate = datenum(y, m, d);
     elseif length(y) == 6
      s = y(6); mi = y(5); h = y(4);
      d = y(3); m = y(2); y = y(1);
      theDate = datenum(y, m, d, h, mi, s);
     else
      theDate = y;
   end
case 3
   theDate = datenum(y, m, d);
case 6
   theDate = datenum(y, m, d, h, mi, s);
otherwise
   error(' ## Incorrect number of arguments.')
end

t0 = datenum(1968, 5, 23) - 2440000;   % May 23, 1968.

t = theDate - t0;
t = [fix(t) rem(t, 1).*24*60*60*1000];

if nargout > 0
   theEpicTime = t;
  else
   disp(t)
end