Neeke

var p = new Ext.Panel({
	width: 800,
	height: 500,
	renderTo: Ext.getBody(),
	items: new Ext.DatePicker({
		//不加这个宽度不会变
		style: 'width:100%;height:100%',
		listeners: {
			'render': function(dp){
				//取得DatePicker的DOM节点的第一个子节点
				var outerTable = dp.el.dom.firstChild;
				//取得DatePicker的顶部导航条
				var tbar = outerTable.firstChild.childNodes[0];
				//取得DatePicker的主体
				var main = outerTable.firstChild.childNodes[1];
				//取得DatePicker底部工具条
				var bbar = outerTable.firstChild.childNodes[2];
 
				var innerTable = main.firstChild.firstChild;
				//
				var thead = innerTable.firstChild;
				//使用行内样式修改
				outerTable.style.width = '100%';
				outerTable.style.height = '100%';
				//以下为解决DatePicker变形
				tbar.style.height = '30px';
				bbar.style.height = '30px';
				innerTable.style.height = '100%';
				thead.firstChild.style.height = '20px';
			}
		}
	})	
});