[Shamun]

That's a bit confusing.

Your first statement is checking the years, then your second is checking the months. It's also not an ifelse statement which would be more logical.

In any case...

function calage()

    {
        var curd = new Date(curyear,curmon-1,curday);
        var cald = new Date(calyear,calmon-1,calday);
        var diff =  Date.UTC(curyear,curmon,curday,0,0,0) - Date.UTC(calyear,calmon,calday,0,0,0);
        var dife = datediff(curd,cald);
        
        if (dife[0]<1) {
            document.getElementById('dAge').innerHTML = dife[1]+" months, and "+dife[2]+" days";
            }
        else {
        document.getElementById('dAge').innerHTML = dife[0]+" years, "+dife[1]+" months, and "+dife[2]+" days";
        }
    }

Tested and works.