SAPUI5: DatePicker defining .setDateValue()

Hello,

as the Title states,

How should .setDateValue() be definied for it to work Properly. A simple String of .setDateValue("Hallo Welt") doesn't work, since it requires an Object as a Parameter.

How .setDateValue() should be definied for it to be working so later on Operations such as .setDate(), can be used ?