Save xtype datefield as Date.

Hello,

I want to save a xtype ‘datefield’ in CQ5 as Date type, like a jcr:created property for example. In dialog node i have defined a ‘cq:widget’  with the property xtype=‘datefiled’. But the issue is that the result is saved like a String type insted of Date type.

How can i save the item as Date?

Thanks !