why does my function keep showing logical 0 for every input?

function valid= valid_date(date,month,year)
    if isscalar(date) && date>0 && month>0 && year>0 && isscalar(year) && isscalar(month) && date==fix(date) && month==fix(month) && year==fix(year)&& month<12 && date<31
        if mod(year,4)==0 || mod(year,400)==0 && mod(year,100)~=0
            if month==2
                if date<=29
                    valid= true;
                else
                    valid=false;
                end
            elseif month==1|| month==3|| month==5|| month==7|| month==8 || month==10  month==12
                   if date<=31
                        valid=true;
                   else
                        valid=false;
                   end
            elseif month==4|| month==6|| month==9|| month==11
                   if date<=30
                            valid=true;
                   else
                            valid=false;
                   end
            end
        else
            if month==2
               if date<=28 
                       valid= true;
               else
                       valid=false;
               end
            elseif month==1|| month==3|| month==5|| month==7|| month==8 || month==10  month==12
                   if date<=31
                        valid=true;
                   else
                        valid=false;
                   end
            elseif month==4|| month==6|| month==9|| month==11
                   if date<=30
                            valid=true;
                   else
                            valid=false;
                   end
            end
        end
    else
                      valid=false;
                      
                       
    end
                  
    
    end

[John D'Errico]

You don't actually tell what inputs you might be passing to this function. I might bet that has something significant to do with your problem.

Answer 1

[Image Analyst]

You're missing a || in two places, like:

elseif month==1|| month==3|| month==5|| month==7|| month==8 || month==10  month==12
                                                                        ^^  

Plus, don't call your variables month, date, and year since those are built-in functions names.