<script type="text/javascript" language="javascript">
 
   function CompareDate() {
       //Note: 00 is month i.e. January
       var dateOne = new Date(2012, 00, 25); //Year, Month, Date
       var dateTwo = new Date(2011, 00, 25); //Year, Month, Date
       if (dateOne > dateTwo) {
            alert("Date One is greather then Date Two.");
        }
           else 
           {
            alert("Date Two is greather then Date One.");
        }
    }
 
    CompareDate();
</script>

var a = new Date();
var b = new Date(a);
var same = a.getTime() === b.getTime();
var notSame = a.getTime() !== b.getTime();

var a = new Date();
var b = new Date(a);

console.log(a == b);   // prints false (wrong!) 
console.log(a === b);  // prints false (wrong!)
console.log(a != b);   // prints true  (wrong!)
console.log(a !== b);  // prints true  (wrong!)
console.log(a.getTime() === b.getTime()); // prints true (correct)

var dates = {
    convert:function(d) {
        // Converts the date in d to a date-object. The input can be:
        //   a date object: returned without modification
        //  an array      : Interpreted as [year,month,day]. NOTE: month is 0-11.
        //   a number     : Interpreted as number of milliseconds
        //                  since 1 Jan 1970 (a timestamp) 
        //   a string     : Any format supported by the javascript engine, like
        //                  "YYYY/MM/DD", "MM/DD/YYYY", "Jan 31 2009" etc.
        //  an object     : Interpreted as an object with year, month and date
        //                  attributes.  **NOTE** month is 0-11.
        return (
            d.constructor === Date ? d :
            d.constructor === Array ? new Date(d[0],d[1],d[2]) :
            d.constructor === Number ? new Date(d) :
            d.constructor === String ? new Date(d) :
            typeof d === "object" ? new Date(d.year,d.month,d.date) :
            NaN
        );
    },
    compare:function(a,b) {
        // Compare two dates (could be of any type supported by the convert
        // function above) and returns:
        //  -1 : if a < b
        //   0 : if a = b
        //   1 : if a > b
        // NaN : if a or b is an illegal date
        // NOTE: The code inside isFinite does an assignment (=).
        return (
            isFinite(a=this.convert(a).valueOf()) &&
            isFinite(b=this.convert(b).valueOf()) ?
            (a>b)-(a<b) :
            NaN
        );
    },
    inRange:function(d,start,end) {
        // Checks if date in d is between dates in start and end.
        // Returns a boolean or NaN:
        //    true  : if d is between start and end (inclusive)
        //    false : if d is before start or after end
        //    NaN   : if one or more of the dates is illegal.
        // NOTE: The code inside isFinite does an assignment (=).
       return (
            isFinite(d=this.convert(d).valueOf()) &&
            isFinite(start=this.convert(start).valueOf()) &&
            isFinite(end=this.convert(end).valueOf()) ?
            start <= d && d <= end :
            NaN
        );
    }
}

var a = new Date('2013-05-23');
var b = new Date('2013-05-23');

// less than, greater than is fine:
a < b; => false
a > b; => false
a === b; => false, oops!

// anything involving '=' should use the '+' prefix
// it will then compare the dates' millisecond values
+a <= +b;  => true
+a >= +b;  => true
+a === +b; => true

var a = new Date(2013, 0, 1);
var b = new Date(2013, 0, 2);
a <  b; // true
a <= b; // true
a >  b; // false
a >= b; // false

var a = new Date(2013, 0, 1);
var b = new Date(2013, 0, 1);
/*
 * note: a == b returns false as described above
 */
a.getTime() == b.getTime(); // true
a.valueOf() == b.valueOf(); // true
Number(a)   == Number(b);   // true
         +a == +b;            // true

var oDateOne = new Date();
var DateTwo = new Date();

alert(DateOne - DateTwo === 0);
alert(DateOne - DateTwo < 0);
alert(DateOne - DateTwo > 0);