Sample Javascript:
   
{!REQUIRESCRIPT(“/soap/ajax/20.0/connection.js”)} 
{!REQUIRESCRIPT(“/soap/ajax/20.0/apex.js”)}


var date1Str = {!YEAR(Sample__c.Sample__c)} + ‘/’ + {!MONTH(Sample__c.Sample__c)} + ‘/’ + {!DAY(Sample__c.Sample__c)};


var date1 = new Date(date1Str);


var date2Str = {!YEAR(Sample__c.Sample__c)} + ‘/’ + {!MONTH(Sample__c.Sample__c)} + ‘/’ + {!DAY(Sample__c.Sample__c)};


var date2 = new Date(date2Str);

if( date2 < date1 ){
    //Logic
} 


Cheers!!!