Date.prototype.dateAdd = function(interval,number) { var d = this; var k={'y':'FullYear', 'q':'Month', 'm':'Month', 'w':'Date', 'd':'Date', 'h':'Hours', 'n':'Minutes', 's':'Seconds', 'ms':'MilliSeconds'}; var n={'q':3, 'w':7}; eval('d.set'+k[interval]+'(d.get'+k[interval]+'()+'+((n[interval]||1)*number)+')'); return d; } Date.prototype.dateDiff = function(interval,objDate2) { var d=this, i={}, t=d.getTime(), t2=objDate2.getTime(); i['y']=objDate2.getFullYear()-d.getFullYear(); i['q']=i['y']*4+Math.floor(objDate2.getMonth()/4)-Math.floor(d.getMonth()/4); i['m']=i['y']*12+objDate2.getMonth()-d.getMonth(); i['ms']=objDate2.getTime()-d.getTime(); i['w']=Math.floor((t2+345600000)/(604800000))-Math.floor((t+345600000)/(604800000)); i['d']=Math.floor(t2/86400000)-Math.floor(t/86400000); i['h']=Math.floor(t2/3600000)-Math.floor(t/3600000); i['n']=Math.floor(t2/60000)-Math.floor(t/60000); i['s']=Math.floor(t2/1000)-Math.floor(t/1000); return i[interval]; }