It doesn't matter that we're already rushing round like cats with their tails on fire. It doesn't matter that we're already breathless with panic – buying Christmas presents, ordering turkeys, stirring Christmas puddings and getting tinsel down from the loft.
Because life as we know it will end on December 25.
Think about it. How often do you say, "We must meet up before Christmas." Why? Does everyone suddenly disappear in a puff of smoke on December 26?
If you haven't seen these particular friends for the whole of the previous year, what makes you so desperate to see them now? Why are you trying to cram in yet another jolly get-together when you're already exhausted from carol concerts, nativity plays and riotous Christmas lunches?
It's no better at work. You're buzzing round like a crazed bluebottle trying to get everything done before people drift off in an alcoholic haze. But there's also that enormous project that someone dreamt up in September when the festive season seemed a long way off.
"Oh, yes," you said at the time. "We can easily get it done by Christmas." Now you're stuck at your PC, mince pie in one hand, paper hat in the other, wondering if you'll still be at work on Christmas Day.
At home the jobs are piling up like recycled rubbish. If you've got family and friends coming to stay, it is, of course, natural to want to chip off some of the limescale blocking up the bathroom tap.
But do you really need to get the whole of the outside of the house painted? The spare room re-decorated? A brand-new sofa delivered (whatever dfs may say)?
"I must get a new carpet before Christmas,'"you say. Why? Just so someone can drop mulled wine on it? Just so that you're down on your hands and knees every five minutes scrabbling for squashed raisins and lost pine needles?
Some of this panic, of course, is whipped up by retailers. (And who can blame them in this current climate – you've got to get your sales from somewhere.) They let you know the clock is ticking. They make sure you realise that time is running out. "Don't forget to buy your crackers!" they shout in August.
But you have to wonder whether all this drama is a bit over-the-top. Your washing machine blows up in November? Go to a high street shop and there will be a sharp intake of breath. Outside there may bonfires and sparklers. But the retailers are already looking ahead to the end of the world as we know it.
"We can't guarantee delivery by Christmas," they say. You look at them in astonishment. Why? Does it have to be brought by sleigh and reindeer?
You want it done by Christmas? You'll have to pay extra. It's like trying to take out health insurance when you're pregnant – completely impossible because all terms and conditions are violated by a cataclysmic forthcoming event.
Last year, at home, all the lights blew on the ground floor. To find the fault, the electrician had to take up the carpet on the landing. (It's not a big landing. Just a few square feet.)
Oh dear, I thought. I don't want my mother-in-law tripping up on that tiny bit of carpet. So I rang round some fitters. Most were booked up. ("I must get a new carpet before Christmas.") But one of them came round, all beaming and friendly like Santa himself, and said he could stretch it back down again for £250.
(In case you're wondering, the landing carpet stayed ruffled and my mother-in-law was persuaded not to go upstairs.)
It's not surprising you snap at anyone who says, "Ready for Christmas?" You can't be ready for Christmas if it means massive expense and forward-planning on the scale of a Royal Wedding.
Take the Big Shop. Every Christmas we buy enough food to see us through until next spring. Why?
Well, the argument goes, because all the shops will be shut for a fortnight.
Except they won't be.
All the big supermarkets throw open their doors as soon as the last drop of rum sauce has been scraped off the plate. We rush out into the cold even though our fridges are bursting with leftover turkey and cold roast potatoes.
It happens every year. But we still behave like manic squirrels stockpiling nuts. We still behave as if we're facing the end of the world, the apocalypse, a nuclear winter.
And what's the result of all this? As any GP will tell you, if you work 200% harder in the run-up to Christmas, your stress levels sky-high, you will be ill on Christmas Day. You will be in bed with a box of tissues and a hot Lemsip listening to the sounds of revelry below.
I don't know – maybe that's the deadline we're all secretly working to. We're desperately trying to get a temperature and a blocked nose. Just so that we can have a bit of peace and quiet.
Does this sound horribly familiar to you?
Are you doing a mad dash towards Christmas or determined to take things more slowly and enjoyably?
More on Parentdish: How to cut corners and save your sanity in the run-up to Christmas