date validation using javascript

Below is the javascript code to validate date

function ChkDate(year) {

    var str=year.split('/');
        if(str.length!=3)return false;

    var date=parseInt(str[0]);
  
    if(isNaN(date))return false;
        if(date==0){
        date=parseInt(str[0].substring(1,2))
    }
  
    var m=parseInt(str[1]);
    if(m==0){
        m=parseInt(str[1].substring(1,2))
    }
  
    if(isNaN(m))return false;
  
    var year=parseInt(str[2]);
  
    if(isNaN(year))return false;
    var daysInMonth = DaysArray(12)
  
    //    var m=monNumFor(month);
    var s=new Date().toString();
    var Arr=s.split(' ');
    for(var i=3;i<Arr.length;i++)
    {
        if(Arr[i].length==4)
        {
            Arr[3]=Arr[i];
        }
    }
    Arr[2]=parseInt(Arr[2]);//date
    Arr[1] =parseInt(monNumFor(Arr[1]));//mon
    Arr[3]=parseInt(Arr[3]);//year
  
    var minYear=Arr[3]-100;
    var maxYear=Arr[3]+100;
  
    if (date<1 || date>31 || (m ==2&& date>daysInFebruary(year)) || date > daysInMonth[m]){
        return false
    }
    if(m<1 || m>12) return false;
    if (year==0 || year<minYear || year>maxYear){
        return false
    }
      
    if (year>Arr[3])
    {
        return false;
    }
    if(year==Arr[3] && m>Arr[1])
    {
        return false;
    }
    if(year==Arr[3] && m==Arr[1] && date>Arr[2])
    {
        return false;
    }
    return true;
}

function daysInFebruary (year){
        return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
}

function DaysArray(n) {
    for (var i = 1; i <= n; i++) {
        this[i] = 31
        if (i==4 || i==6 || i==9 || i==11) {this[i] = 30}
        if (i==2) {this[i] = 29}
   }
   return this
}

function monNumFor(m)
{
        switch(m)
    {
        case "Jan":
            m ="1";
            break;
        case "Feb":
            m ="2";
            break;
        case "Mar":
            m ="3";
            break;
        case "Apr":
            m ="4";
            break;
        case "May":
            m ="5";
            break;
        case "Jun":
            m ="6";
            break;
        case "Jul":
            m ="7";
            break;
        case "Aug":
            m ="8";
            break;
        case "Sep":
            m ="9";
            break;  
        case "Oct":
            m ="10";
            break;
        case "Nov":
            m ="11";
            break;
        case "Dec":
            m ="12";
            break;
    }
    return m;
}