Oops, thanks for letting me know. I've corrected it and pushed the change to the source code repository.
Note that it is also possible to configure it for existing features. For example to show the year and month selectors in the date picker used for blog posts you can put this in the theme.skin file of your skin.
<mp:DatePickerControl runat="server" SkinID="blog"
ShowMonthList="true"
ShowYearList="true"
/>
Note that for DatePickers without a skinid you just add another one to theme.skin without the skinid property like this:
<mp:DatePickerControl runat="server"
ShowMonthList="true"
ShowYearList="true"
/>
For other specific features you may need to look at the existing control declaration to determine what if any skinid it has.
Best,
Joe