The default format for dates is chosen based on your locale. To change this format:
in the preferences dialog, in the tree, expand View preferences, and General, and select Date format.
in the right hand panel, select your format.
Note that this will change the setting in all columns, tooltips and reports. You can override this setting for a specific column as described here. You can also create custom date formats using this option. Date input will be based on the format chosen here.