Illicit sickies.
You can't do anything fun with the time in case you get seen out on your bike/at the seaside/down the pub or someone decides to check up on you. The test match/wimbledon etc. always gets rained off on that day or the only decent film on telly is cancelled as the news over-ran because of the queen's official birthday celebrations from sandringham (yawn). The next door neighbour always has builders/tree surgeons in, their dog never stops barking/child never stops wailing. The electricity board/water board disconnects the power/water supply for essential work. There's no nice snacks in the cupboard or beer in the fridge, even if you put them there the night before.
Just end up being bored, grumpy and wishing you'd gone to work and when you do go back you've still got all the work to do and less time to do it.
You need another day off sick to recover!