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;
}