How do I set the initial day for a DatePicker - google-apps-script

Question

I have two DatePicker objects on a Web UI.
Initially the first should display a day in the past (like january 1st 2010), the second should display the current day (and it does).
I use
var oldDatePicker = myApp.createDatePicker();
var oldDate = new Date(2010, 1, 1);
oldDatePicker.setValue(oldDate);
but that doesn't work
How can I initialize my oldDatePicker?
EDIT 1 --> example
The lines
var zoekBeginDatum = new Date(2012, 8, 15);
pickerBeginDatum.setValue(zoekBeginDatum);
do not provide the desired result
The full (demo) code of the not working example is:
// Global CONSTANTS to be used for initialization
var globalBeginDatum = '2010/04/24';
var globalEindDatum = '';
var globalUseDatums = 'false';
function doGet()
{ // A script with a user interface that is published as a web app
// must contain a doGet(e) function.
// Create 'global' variables, accesible only by this script
var userProperties = PropertiesService.getUserProperties();
userProperties.setProperty('globalBeginDatum', globalBeginDatum);
userProperties.setProperty('globalEindDatum', globalEindDatum);
userProperties.setProperty('globalUseDatums', globalUseDatums);
// Create the UiInstance object myApp and set the title text
var myApp = UiApp.createApplication()
.setTitle('Test datePicker initialvalue')
.setHeight(50)
.setWidth(100);
var breedteTextBox = 600;
var gridTexts = myApp.createGrid(3, 2);
var labelBeginDatum = myApp.createLabel('Begindatum').setId('labelBeginDatum');
var labelEindDatum = myApp.createLabel('Einddatum').setId('labelEindDatum');
var pickerBeginDatum = myApp.createDatePicker().setId('pickerBeginDatum').setName('pickerBeginDatum');
var zoekBeginDatum = new Date(2012, 8, 15); // Initial date for searching ---> does NOT work
pickerBeginDatum.setValue(zoekBeginDatum);
var pickerEindDatum = myApp.createDatePicker().setId('pickerEindDatum').setName('pickerEindDatum');
var zoekEindDatum = new Date(); // Current date
pickerEindDatum.setValue(zoekEindDatum);
var gridDatum = myApp.createGrid(2, 3);
gridDatum.setWidget(0, 1, labelBeginDatum);
gridDatum.setWidget(0, 2, labelEindDatum);
gridDatum.setWidget(1, 1, pickerBeginDatum);
gridDatum.setWidget(1, 2, pickerEindDatum);
var gridOptions = myApp.createGrid(9, 1);
var onClickChkDatums = myApp.createServerHandler('onClickChkDatums');
var chkDatums = myApp.createCheckBox('Gebruik de begindatum en de einddatum bij het zoeken')
.setId('chkDatums').setName('chkDatums')
.addClickHandler(onClickChkDatums);
gridOptions.setWidget(4, 0, chkDatums);
// Create a vertical panel called verPanel and add it to myApp
var verPanel = myApp.createVerticalPanel().setWidth('60%').setBorderWidth(2).setStyleAttribute('background', 'lightyellow');;
var horPanel = myApp.createHorizontalPanel().setWidth('100%').setStyleAttribute('background', 'lightcyan');
horPanel.add(gridOptions);
horPanel.add(gridDatum);
verPanel.add(horPanel);
labelBeginDatum.setVisible(globalUseDatums == 'true');
labelEindDatum.setVisible(globalUseDatums == 'true');
pickerBeginDatum.setVisible(globalUseDatums == 'true');
pickerEindDatum.setVisible(globalUseDatums == 'true');
// Center verPanel by adding it to another panel occupying whole browser window
var fullPanel = myApp.createVerticalPanel().setStyleAttribute('background', 'beige');
fullPanel.setHeight('100%');
fullPanel.setWidth('100%');
fullPanel.setHorizontalAlignment(UiApp.HorizontalAlignment.CENTER);
fullPanel.setVerticalAlignment(UiApp.VerticalAlignment.MIDDLE);
fullPanel.add(verPanel);
myApp.add(fullPanel); // Now verPanel will be centered
return myApp;
}
// *************** Eventhandlers
function onClickChkDatums(e)
{ // Eventhandler for chkDatums
var app = UiApp.getActiveApplication();
var chkDatums = app.getElementById('chkDatums');
var status = (e.parameter.chkDatums == 'true');
var labelBeginDatum = app.getElementById('labelBeginDatum');
var labelEindDatum = app.getElementById('labelEindDatum');
labelBeginDatum.setVisible(status);
labelEindDatum.setVisible(status);
var pickerBeginDatum = app.getElementById('pickerBeginDatum');
var pickerEindDatum = app.getElementById('pickerEindDatum');
pickerBeginDatum.setVisible(status);
pickerEindDatum.setVisible(status);
var userProperties = PropertiesService.getUserProperties();
userProperties.setProperty('globalUseDatums', status);
return app;
}

Answer 1

I don't want to make it a habit answering my own questions, but this one might be useful for others as well.
Using BOTH setCurrentMonth() and setValue() shows the right dates in the datePicker
pickerBeginDatum.setCurrentMonth(zoekBeginDatum); // Needed !!
pickerEindDatum.setCurrentMonth(zoekEindDatum); // Needed !!
pickerEindDatum.setValue(zoekEindDatum); // Does ONLY work in combination with setCurrentMonth
pickerBeginDatum.setValue(zoekBeginDatum); // Does ONLY work in combination with setCurrentMonth