function d = dy2date(y)
% DY2DATE   - Decimal year to serial date number
%
% Use as: SerialDateNumber = dy2date(DecimalYear)
% Inputs: DecimalYear = The date in years 
%         (ex. 1998.345 = 
% Output: SerialDateNumber = Matlab method of storing dates
%
% See Also: DATENUM, DATESTR, DATEVEC

% Brian Schlining
% 22 Dec 1998
% 07 Jan 1998; changed p8 = max(find(p1 > days)) to p8 = max(find(p1 >= days)); This 
% was done because certain whole numbers (ex. 99) would return empty to p8

YEAR = floor(y);
if isleap(YEAR)
   DaysPerYear = 366;
else
   DaysPerYear = 365;
end

DAY  = (y - YEAR)*DaysPerYear;
[rD cD] = size(DAY);
for r = 1:rD
   for c = 1:cD
      [date y1 mo1 d1] = caldate_(DAY(r,c),YEAR(r,c)); 
      d(r,c) = datenum(y1,mo1,d1+1);         % There's a one day offset, correct by adding 1
   end
end


%%%%%%%%%
% ISLEAP
%%%%%%%%%
function p = isleap(year)
if rem(year,4) == 0
   p = 1;
else
   p = 0;
end

%%%%%%%%%%%
% CALDATE_
%%%%%%%%%%%
function [p2,p6,p8,p9,h,mn,s,yy] = caldate_(p1,option)

if nargin > 1
   if option == 0 
      Feb = 28;
      p6  = nan;
   elseif option == 1  
      Feb = 29;
      p6  = nan;
   else 
      if rem(option,4) == 0    % Then these are leap years
         p6  = option;          % pass year in as option
         Feb = 29;
      else
         p6 = option;      
         Feb = 28;                   
      end
   end
   
   daymon = [0 31 Feb 31 30 31 30 31 31 30 31 30 31];
   days   = cumsum(daymon);
   p8     = max(find(p1 >= days));    % month
   p9     = p1 - days(1, p8);        % day of month
   p2     = p9 + p8/100;             % DD.MM 
   if p8 > 12
      disp('CALDATE_ Error Invalid Julian Day')
   end 
   h = nan; mn=nan; s=nan; yy = nan;
   return
else
   [a,b] = size(p1); 
   if(a > 1) 
      p1 = p1'; 
   end   
   p3 = rem(p1 + 0.5,1);                 % julian days 
   p4 = floor(p1 + 0.5); 
   i1 = find(p4 >= 2299161); 
   if any(i1) 
      p5(i1) = floor((p4(i1) - 1867216.25)./36524.25); 
      p4(i1) = p4(i1) + p5(i1) + ones(size(i1)) - floor(p5(i1)/4);
      
   end; 
   p5 = p4 - 1720995; 
   
   yy = (p5 - 122.1)./365.25; 
   
   p6 = floor((p5 - 122.1)./365.25);     % year 
   p7 = floor(365.25.*p6); 
   p8 = floor((p5-p7)./30.6001);         % month 
   p9 = p5 - p7 - floor(30.6.*p8); 
   p10 = floor(p9 + p3);                 % day of month; 21Jun96 round -> floor  
   i2 = find(p8 >= 14);                  % must make both tests before changing p8 
   i3 = find(p8 < 14); 
   if any(i2) 
      p8(i2) = p8(i2) - 1 - 12; 
   end 
   if any(i3) 
      p8(i3) = p8(i3) - 1; 
   end 
   i4 = find(p8 < 3);                    % if Month is less than 3 add one year 
   if any(i4) 
      p6(i4) = p6(i4) + 1; 
   end; 
   
   p2 = (p6 - 1900)./10000 + p8./100 + round(p10); % pack into DD.MMYY 
   
   h  = 24*p3; 
   m  = (h - floor(h))*60; 
   s  = (m - floor(m))*60; 
   h  = floor(h);            % hour 
   mn = floor(m);            % minute 
   s  = floor(s);            % second 
   if(a > 1)            % columns input so make output columns too
      
      p1 = p1'; 
      p2 = p2'; 
      p6 = p6'; 
      p8 = p8'; 
      p9 = p9'; 
      h = h'; 
      m = m'; 
      s = s'; 
      mn = mn'; 
   end   
end