So it's September now, and September works like this: you aren't supposed to want the summer to be over, so you sigh about August coming to a close. Ugh, back to work, you say. Something about having to wear a coat, something about routine, something about considering chewing off your own tongue with the drudgery of it all. Why can't it be summer for ever, you mutter. When the fact is that September is the finest month of the year, and deep down we all know this to be true.

Especially if you ever went to France as a child and quivered with joy in one of their stationery shops, where the words la rentrée indicated the back-to-school march as if it were a quasi-religious festival. (We'll ignore the fact that all their notebooks were made of squared paper and that every French person ended up with the exact same handwriting – I've always wondered how hard it must be to make a living as a graphologist in France.)

It's not as if I actually liked school – I really didn't. I just liked getting ready for school, each year imagining how perfect it might be this time. Exercise books not yet ruined by scratchy red marks. The shiny, new, unscuffed shoes of the mind. The chance to be handed a brand-new timetable, moved up a year and given official confirmation that yes, you have grown. I still have that back-to-school feeling – no other time of year has the power to make me want to buck my ideas up and get my uniform ready. So ingrained in our seasonal bodyclocks is it that even grandparents are currently getting wistful about pencils being sharpened, new school shoes being bought and name tapes being sewn into collars. All right, so no child has actually used a pencil since John Major left office, you can't sharpen an iPad and name tapes aren't necessary now uniforms are hologrammed directly on to children's bodies from the coalition government's bureau of central control. But who doesn't long for the clean white page of the new term, when you have a fresh stab at inventing yourself, and nothing has gone embarrassingly wrong yet? If you were lucky enough to have a childhood that involved new pencil cases and stationery sets, then you know the basic sensation of being rich.

I mean, August may have given us such a good summer that it actually felt shaggable – thanks, British weather gods, those live human sacrifices we made during the eight-month winter of pain and devastation were all worth it in the end – but still. If August was shaggable, September is the post-coital cigarette. It's a Gauloise in the afterglow. In fact, September just walked in wearing a crisp linen suit that doesn't crumple when you sit down. It carries its blessings lightly, no expectation, just gratitude that some warmth still lingers in the air. It is summer's temperate ghost.

Of course maybe I'm wrong. Maybe your summer was wild and exotic and you had a passionate affair with a fisherman on a remote island where the waters were crystal-clear turquoise, a thousand fathoms deep. Or maybe you went on a holiday where you were reduced to playing a mental game of shag-marry-kill all by yourself, and just involving three members of your own family, because a week had passed since you had so much as looked at anyone with unfamiliar chromosomes. Maybe the weather being so good for once meant that you couldn't moan about it as usual, and instead had to tell people what was really bothering you, which, in turn, accidentally led to the dissolution of your business and the end of your marriage. Or maybe summer, in your head, is always the montage scene of a film character who you think is going to be you, so bronzed and free, but it never, ever is.

Don't worry about it – for now you have September. Yes, there will be memorials for all of those who died at the World Trade Center, and there will be anger, and there will be pain. There will be wars and poverty – apparently we haven't solved those yet. But there will also be harvest festival, when children bring tins of food to school and think about farmers. And the Chinese moon festival. And did you know that in 1752, when the British empire adopted the Gregorian calendar, 11 fiddly days had to be got rid of first? Which is why the nation went to bed on Wednesday 2 September and woke up on Thursday 14 September. I'm not sure they'd get away with that now.

Forget Easter, or Christmas – there is something so alluring about the autumnal way of starting afresh. "How have I only just discovered running?" said my friend S this morning. "I feel like an octopus that has just been born!" You see, this is even the perfect month to get fit – quick, do it now before they have to salt the pavements. Because January, when the rates for both divorce and suicide rocket, and when your innards are four parts goose fat to one part eggnog, is clearly not the safest time of year to be test-driving new versions of yourself. Don't make your new year resolutions in those dark depressing days – it's no wonder nobody actually sticks to them. Start your new year now, and get ahead of all those fools who think it begins in January.