According to blogger and flickrer KimMcK, it means clean out your fridge day. You know why, to get that 18 lb beast in amongst the bags of cranberries, the celery and the brussels sprouts that you always make and end up in the dogs dinner.
I cleaned mine out a few weeks ago while TH was in Hawaii. Its pretty clean now, we have methodically been eating chard, pork chops and eggs to make room for goose, fennel and hubbard squash.
I can see to the back, this is a good thing.
It really doesn't take too much time and if you are really clever, you can photodocument it.