js中用FR.remoteEvaluate来转换
============
var bdate=this.options.form.getWidgetByName("开始日期");
var edate=this.options.form.getWidgetByName("结束日期");
var bvalue= FR.remoteEvaluate('=FORMAT(DATEDELTA("'+bdate.getValue()+'",-1),"yyyy-MM-dd")');
var evalue= FR.remoteEvaluate('=FORMAT(DATEDELTA("'+edate.getValue()+'",-1),"yyyy-MM-dd")');