Vice-like it may be, but the Poorhouse is always up for a flutter - especially when he always wins. However, the below might be the finest sure bet he's had the pleasure of placing.
Sadly it was limited to a tenner, but assuming not even the relatively mighty William Hill (well, you should see the other sorts of places he throws gambling money through) can literally change the calendar, the Poorhouse looks forward to a bonus 10 shiny gold coins on Christmas day. Assuming the confidence is well-placed that is: actually 1000-to-1 was offered on "any other day" so theoretically a guarenteed-win dutch was in order. Risk-takers anonymous here we come.
But how to know when it is actually Christmas day? No need to trust calendars, or even the common sense flowing through humanity for the past couple of thousand years. For all you other readers who need live second-by-second updates on the Christmas situation, may we recommend isitchristmas.com.
(If you already have a WillHill account then wham yourself over there quickly and you might get in on the action. They're only taking 10000 or so bets on this selection though, so it's probably gone by the time this is posted knowing the greedy gamuts in the gambling world.)

Comments
Christmas Boredom
I really liked the 'is it Christmas' site....so much so that I did actually visit it on Christmas day. (There was not much else going on that day. KFC was closed. I did walk head down into the garage door - unintentionally - with enough pace to split my scalp a little. And still I remembered to check the site for an update.) It was amazingly accurate.
Thanks, as always, for keeping me up to date with all the need-to-know stuff and handy resources out there!
Bleeding head injuries, and
Bleeding head injuries, and even KFC refusing to serve you - that is one amazing Xmas! I'm glad you were still connected enough to the world to ensure the site ran correctly. I'd hate to have linked to a lie. Perhaps a "IsKFCOpen.com" is on the agenda for future usefulness?
In the mean time there is also the vague but seemingy truthful whatdayitis.com to keep track of all those non-festive days.