Date picker doesn't work in italian

Steps to reproduce:
1. start the archetype CMS
2. login with language 'Italian'
3. open a news document

Expected: the news document is opened
Actual: the following error is logged:

16.12.2013 15:32:59 ERROR http-bio-8080-exec-1 [DefaultExceptionMapper.internalMap:123] Unexpected error occurred
org.apache.wicket.WicketRuntimeException: Exception in rendering component: [YuiDateTimeField [Component id = widget]]
at org.apache.wicket.Component.internalRenderComponent(Component.java:2575)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1484)
at org.apache.wicket.markup.html.panel.FragmentMarkupSourcingStrategy.onComponentTagBody(FragmentMarkupSourcingStrategy.java:84)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1484)
at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.markup.repeater.AbstractRepeater.renderChild(AbstractRepeater.java:107)
at org.apache.wicket.markup.repeater.AbstractRepeater.onRender(AbstractRepeater.java:94)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1484)
at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.markup.repeater.AbstractRepeater.renderChild(AbstractRepeater.java:107)
at org.apache.wicket.markup.repeater.AbstractRepeater.onRender(AbstractRepeater.java:94)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1484)
at org.apache.wicket.markup.html.form.Form.onComponentTagBody(Form.java:1683)
at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1484)
at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.ajax.XmlAjaxResponse.writeComponent(XmlAjaxResponse.java:127)
at org.apache.wicket.ajax.AbstractAjaxResponse.writeComponents(AbstractAjaxResponse.java:212)
at org.apache.wicket.ajax.AbstractAjaxResponse.writeTo(AbstractAjaxResponse.java:144)
at org.apache.wicket.ajax.AjaxRequestHandler.respond(AjaxRequestHandler.java:363)
at org.hippoecm.frontend.PluginRequestTarget.respond(PluginRequestTarget.java:138)
at org.apache.wicket.request.cycle.RequestCycle$HandlerExecutor.respond(RequestCycle.java:861)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:64)
at org.apache.wicket.request.RequestHandlerStack.execute(RequestHandlerStack.java:97)
at org.apache.wicket.request.cycle.RequestCycle.execute(RequestCycle.java:261)
at org.apache.wicket.request.cycle.RequestCycle.processRequest(RequestCycle.java:218)
at org.apache.wicket.request.cycle.RequestCycle.processRequestAndDetach(RequestCycle.java:289)
at org.apache.wicket.protocol.http.WicketFilter.processRequestCycle(WicketFilter.java:259)
at org.apache.wicket.protocol.http.WicketFilter.processRequest(WicketFilter.java:201)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:282)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.hippoecm.frontend.plugins.login.ConcurrentLoginFilter.doFilter(ConcurrentLoginFilter.java:54)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)
Caused by: java.lang.IllegalArgumentException: Illegal pattern component: g
at org.joda.time.format.DateTimeFormat.parsePatternTo(DateTimeFormat.java:559)
at org.joda.time.format.DateTimeFormat.createFormatterForPattern(DateTimeFormat.java:682)
at org.joda.time.format.DateTimeFormat.forPattern(DateTimeFormat.java:170)
at org.hippoecm.frontend.plugins.yui.datetime.YuiDateTimeField$7.getFormat(YuiDateTimeField.java:243)
at org.apache.wicket.datetime.DateConverter.convertToString(DateConverter.java:148)
at org.apache.wicket.datetime.DateConverter.convertToString(DateConverter.java:43)
at org.apache.wicket.Component.getDefaultModelObjectAsString(Component.java:1680)
at org.apache.wicket.Component.getDefaultModelObjectAsString(Component.java:1652)
at org.apache.wicket.markup.html.form.FormComponent.getModelValue(FormComponent.java:1289)
at org.apache.wicket.markup.html.form.FormComponent.getValue(FormComponent.java:878)
at org.apache.wicket.markup.html.form.TextField.onComponentTag(TextField.java:108)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2519)
at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1493)
at org.apache.wicket.Component.internalRender(Component.java:2378)
at org.apache.wicket.Component.render(Component.java:2306)
at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1554)
at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1529)
at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
at org.apache.wicket.Component.internalRenderComponent(Component.java:2548)
... 160 more