Sorry, I don't use clock widgets.

 

I just checked on mine, and it shows the full date. I thought at first it was the date format but when I changed it, it did NOT affect the flip clock format, so it can't be that. I'm sorry that's no help but at least it closes one avenue.

 

Try going into the clock widget then thru menus World Clock / Local Time Settings / Select Date Format......

You can set whatever format of date you want to - should sort your issue perhaps?