It's the day when the world turns a particularly lurid shade of emerald.
Rivers run green and monuments around the globe, from the Egyptian Pyramids to the Little Mermaid statue in Copenhagen, are lit up the colour of a hallucinogenic shamrock.
Cartoon Oirishness abounds in the form of outsized velveteen leprechaun hats, shillelaghs, fake beards and drinking so much Guinness that you boak in the gutter. This is St Patrick's Day in the 21st century.
Like Halloween, the Americans took it and sold it back to us, with added hype, sentimentality and glitter. Just as turnip lanterns and bobbing for apples in the candlelight have been ditched in favour of plastic pumpkins and crowds of sugar-addled trick-or-treaters, so, too, has St Patrick's Day been turned into a vacuous, global tack-fest – a shameless celebration of the twinkly, gormless stereotype and that magical, mythical entity, 'the craic'.
You might have got the impression that I'm not too keen on the public face of St Patrick's Day. And you'd be right. So I don't get involved in the festivities.
On Sunday afternoon, I had my own private celebration, in the bath, with a glass of Jameson and a book of poems by the Derry poet Robert Greacen.
My daughter, on the other hand, went into town with her mates and had a whale of a time at the parade and concert at Custom House Square. She returned some hours later, rain-bedraggled and laughing, wearing a green net mini-skirt.
That's grand, as far as I'm concerned. Just because I don't enjoy the St Paddy's excess doesn't mean it should be banned in our house. If you don't like it, don't go. If you do like it, go right ahead.
That's an option that's rarely exercised in Northern Ireland. In fact, some people actively go out of their way to sniff out opportunities to take offence.
They willingly expose themselves to the very thing that enrages and antagonises them, just so they can enjoy that warm feeling of self-righteous indignation, that special glow you only get when your most deeply held prejudices are confirmed.
Of course, if you're determined to keep looking hard enough, you're going to find exactly what you need. Occasions like St Patrick's Day and the Twelfth of July – ostentatious, occasionally aggressive and absurdly camp manifestations of national identity – provide ample opportunities.
That's why you have people like Jim Allister and members of the Progressive Unionist Party getting antsy over a newspaper report on Sunday's St Patrick's parade, the source of which was a single, anonymous shopper, claiming that Belfast city centre was awash with "dozens of tricolour-draped teenagers" singing IRA songs.
Now, I have no doubt that there was a sectarian element among the crowd: hell, it wouldn't be a high day or holiday in Northern Ireland if there wasn't.
There will always be some idiots who believe that it's highly subversive and amusing to shout stupid, inflammatory slogans like 'Up the 'Ra'' on these occasions.
It's exactly the same on the Twelfth, which tends to brings out the swaggering supremacist in certain thugs, especially when the blue WKD gets flowing and the Kick the Pope melodies start ringing in their ears.
But what I object to is the eagerness, by people from both sides who should know better, to go looking for trouble, which they can then carry aloft back to their tribe, like a glittering trophy, as evidence to shore up their collective hostility.
Here, they say, look what themmuns have been getting up to now. And that's how the sick old continuum of hatred and suspicion is perpetuated, generation after generation.
Instead of obsessing over who waved a particular flag, or sang a particular song, on St Patrick's Day, or the Twelfth, we should be more concerned about ordinary issues of social responsibility, such as under-age drinking on the streets.
We must wean ourselves off the habit of constantly staring at our little world through the dark, distorting prism of sectarianism. There are too many people in this country who are offended by everything and ashamed of nothing. It is our own home-grown curse.
Last Sunday, I read this old poem by Robert Greacen. Its appeal is as resonant today as the day it was written. It's called A Wish For St Patrick's Day:
Holy Patrick, we need snakecharmers now,
The snakes have crawled back again.
Exorcise the demons of intransigence,
Send your green fire into the frozen branch.