NEW YORK CITY ? It may not be officially marked on the calendar, but Jan. 24 happens to be THE worst day of the year.

Armed with an actual equation, Cliff Arnall, a British psychologist, tallied up all the rotten things we humans must face in life and determined that they happen to peak in late January.

First, there is Jan. 24’s distance from Christmas: way too far to look forward to, but way too recent to have recovered from financially. The misery of debt figures heavily in his equation.

So does weather. Late January weather is amazingly bad compared with pretty much all of spring, summer and fall.

By now, Arnall figures, you have abandoned all your New Year’s resolutions. You are smoking, drinking and overeating – possibly all at once. That’s part of what makes Jan. 24 stink.

And finally, there is the issue of what we have to look forward to: not much. The short-term horizon is distressingly free of three-day weekends or summer blockbuster movies.

That leaves us with tax forms on the way and more predictions of bad weather.