EXTjs中只显示年月时31号问题

用Ext写的页面，只能选择年月的日历，当天是31好时会出现的时间与选择不符。

自定义继承DateField来自网友分享，如下代码：

	//双击时只显示年月
   	DateFieldEx = Ext.extend(Ext.form.DateField, { 
		onTriggerClick : function() {
			DateFieldEx.superclass.onTriggerClick.call(this, arguments); 
			if (this.format.indexOf('d') == -1) { 
				this.menu.picker.monthPicker.slideIn = function() { 
					this.show(); 
				}
				this.menu.picker.hideMonthPicker = function() { 
					this.monthPicker.hide();
					var d = this.activeDate; 
					if (d) { 
						this.setValue(this.activeDate); 
						this.fireEvent('select', this, this.value); 
					}
				}
				this.menu.picker.showMonthPicker(); 
			} 
		} 
	}) ;
   	var cxyd = new DateFieldEx({
   		"anchor" : "90%",
		"selectOnFocus" : true,
		"name" : "cxyd",
		"fieldLabel" : "查询月度",
		"format" : "Y-m",
		"altFormats" : "Y-m-d H:i:s|m/d/Y|n/j/Y|n/j/y|m/j/y|n/d/y|m/j/Y|n/d/Y|m-d-y|m-d-Y|m/d|m-d|md|mdy|mdY|d|Y-m-d",
		"editable" : false,
		"labelStyle" : "color:red"
   	});
	cxyd.document = panel;

在js代码中前增加一行代码就可以解决：

Date.defaults.d = 1;

个人花了半天google加百度悟出来的。

那位大牛友更好的解决只显示年月问题的，望不吝指教。谢谢