Just try following Code. This is working for me.
var win = Titanium.UI.createWindow({backgroundColor:"#f0f"});
var win_list = Titanium.UI.createScrollableView({
backgroundColor:'transparent',
borderWidth:8,
borderColor:'#888',
height:550,
width:330,
top: 180,
zIndex:1,
borderRadius:10,
showPagingControl:true,
pagingControlHeight:30,
});
var view2 = Ti.UI.createView({
left: 0,
width : "90%",
height: '100%',
layout: 'vertical',
zIndex: 10
});
var pickerScore = Titanium.UI.createPicker({
top: 10,
height: 'auto',
type : Ti.UI.PICKER_TYPE_DATE,
});
view2.add(pickerScore);
win_list.addView(view2);
win.add(win_list);
win.open();