Date Validation error in semantics

I am not getting the proper result from this code. At the same time haven't been able to find my errors..

function valid=valid_date(year,month,day)
if integer(year,month,day)==2
    if leap_year(year)==2
        if month>0 && month<12
            if month==2
                if day>29 || day<1
                    valid=false;
                    return
                else
                    valid=true;
                    return
                end
            elseif month==1||month==3||month==5||month==7||month==8||...
                    month==10||month==12
                if day>31 || day<1
                    valid=false;
                    return
                else    
                    valid=true;
                    return
                end
            else 
                if day>30 || day<1
                    valid=false;
                    return
                else
                    valid=true;
                    return
                end
            end
        else
            valid=false;
            return
        end   
    else
        if month>0 && month<12
            if month==2
                if day>28 || day<1
                    valid=false;
                    return
                else
                    valid=true;
                    return
                end
            elseif month==1||month==3||month==5||month==7||month==8||...
                    month==10||month==12
                if day>31 || day<1
                    valid=false;
                    return
                else    
                    valid=true;
                    return
                end
            else 
                if day>30 || day<1
                    valid=false;
                    return
                else
                    valid=true;
                    return
                end
            end
        else
            valid=false;
            return
        end   
    end
else
    valid=false;
    return
end    
function result1=integer(year,month,day)
        if ~isscalar(year) || year<1 || year~=fix(year)||...
           ~isscalar(month) || month<1 || year~=fix(month)...
           ~isscalar(day) || day<1 || year~=fix(day)
            result1=1;
        else
            result1=2;
        end

function result2=leap_year(year)
        if mod(year,400)==0 || (mod(year,4)==0 && mod(year,100)~=0)
            result2=1;
        else
            result2=2;
        end
       

Answer 1

[Ameer Hamza]

Why not use built-in MATLAB's function

function isValid = dateVal(year, month, date)
    dt = datetime(year, month, date);
    [y,m,d] = ymd(dt);
    isValid = isequal([y, m, d], [year, month, date]);
end

Example:

K>> dateVal(1900, 2, 29)
ans =
  logical
   0
K>> dateVal(2000, 2, 29)
ans =
  logical
   1

[Anowarul Faruk Shishir]

It was a task where using built in function was prohibited

[Ameer Hamza]

Try to use breakpoint: https://www.mathworks.com/help/matlab/matlab_prog/set-breakpoints.html and run your code line by line. It will help in finding out which conditions are causing problems.