Fractions can be added and subtracted only if they're fractions

Check the explanation

Step-by-step explanation:

function [valid]=valid_date(y, m, d)

if ~isscalar(y)  || ~isscalar(m)  || ~isscalar(d)  

   valid=false;

   return

end

   if y>=1 && m>=1 && m<=12  && (ismember(m, [4 6 9 11]) && ismember(d, [1:30])) || (ismember(m, [1 3 5 7 8 10 12]) && ismember(d, 1:31))  

   valid=true;

elseif m==2 && (mod(y,4)==0 && mod(y,100)~=0 || mod(y,400)==0 && mod(y,100)==0) && ismember(d, 1:29)  

       valid=true;

   elseif m==2 && ismember(d, 1:28)  

       valid=true;

   else

       valid=false;

       return

   end

end