Date.getDay() javascript returns wrong day

I have such javascript code

alert(DATE.value);
var d = new Date(DATE.value);
var year = d.getFullYear();
var month = d.getMonth();
var day = d.getDay();
alert(month);
alert(day);
if(2012 < year < 1971 | 1 > month+1 > 12 | 0 >day > 31){
    alert(errorDate);
    DATE.focus();
    return false;
}

take for instance: DATE.value = "11/11/1991"

when I call alert(day); it shows me 3;
when I call alert(d); it is returns me correct info.