Hi Robin,
It did not work for me like that either.
But I did find a solution for this,
Taking a close look at my date format - yyyyMMdd which is fixed, I have a source which is not compatible to the locale. Hence I need a way to define the source pattern too. And I tried the following in the template
template: new sap.ui.commons.DatePicker({
value:{
path : "DeliverDate",
type : new sap.ui.model.type.Date({source: {pattern: "yyyyMMdd"}, pattern: "dd.MM.yyyy"})
}
})
works and displays 22.07.2014 for the incoming String 20140722.
When I send this data back to the server, I do not need any conversion, as I have the date patterned in the way the backend needs.
Sincere thanks to you for making me think 
cheers
Domnic