29/04/2013 13:31 BST | Updated 29/06/2013 06:12 BST

When Did Nineties Kids Become So Old?

I have been thinking about adulthood recently. Partly because I recently turned 21 and have a grim, grey-suited cloud of graduate opportunities approaching. But mainly because I have exams, and getting into extended philosophical debates with oneself is more interesting than economic history.

An old school friend's little sister recently popped up in my Facebook feed. She was in a thigh-length, turquoise dress, had a cocktail in one hand and a boy in the other: "Imagine if her parents saw!", I thought. Who would have expected the sweet girl who once asked me out (one of only four girls to make such a mis-judgement) was now an underaged drinker, boys lusting over her like pigs for the trough?

But on routing into her apparent rebellion, I made a horrifying discovery. One of those uncomfortable, life-enhancing epiphany sort of moments. She was not underage. She could drink and smoke and do whatever it is men and women do with each other, and it would all be legal. Somehow, some way, kids born in 1995 became 18. 

It ought to have been a simple matter of maths. But the revelation that, not only am I an adult, but my friends' little siblings - the kids I once babysat - were also now old enough to get trollied, hitched and have a night at Gala Bingo, felt wrong. Christ, kids still in primary school when I was sitting GCSE exams can now have their own kids. The babies of, er, 1999 are old enough to join the Labour party (or the Tories, if they're into that). 

But what makes us an adult, really? What actually changes as we go from the final days of the 17th year, into beer-guzzling, bet-placing, bill-paying maturity? 

It would be a lie to suggest that nothing changes. I no longer throw extended, highly emotional screaming matches at being forced to eat sprouts, like I did when I was 12. Or wet the bed, like I did when I was 12. But fundamentally, it doesn't feel so different. I for one prefer a Tracey Beaker omnibus and ice cream to paying bills.

In fact I'm not convinced we really grow up. We accumulate years, yes, and frequently we accumulate weight (I'm not yet at the stage to accumulate age lines, like Cher), but the expectations society places on us from the early moments of that 18th year, are not the real arbiter of age.

Adulthood is when the changing of your favourite colour - from blue to orange, in my case - is not just the consequence of some TV fad or comic book, but a sign of a fundamental emotional change for which people will suggest we should probably seek help. The adult expectations are there to pen us in to meaningless platitudes and pleasantries - and we're not even allowed to be fascinated by how shiny the pen is. Maturity is the departure from playing with the box, to learning to sit in it.

Ageing does have its oddities. I remember, last summer, seeing a handsome man in a club whom I thought I knew vaguely, and coming on to him. Afterwards my friend explained that I did know him, in some way - he was a kids' TV presenter. From when I was a kid. But this did not fetch for a call to Operation Yewtree. No, in fact he wasn't so many years older. Suddenly it became apparent that when I say I'm interested in '18-35-year-olds', that includes the guy who taught me times-tables, my babysitter, or, in this case, the bloke who introduced Dennis the Menace on CBBC.

When you're a kid, all the world will encourage you to pursue your dreams:"You want to be a fireman, Benji? You'd be a great fireman, Benji!" But when you're an adult, people become offended, somehow, by the very suggestion. "You want to be a fireman, Benji? You'd look ridiculous. You puff." (Not a direct quote, for the defence of my family. But it's what they'd be thinking.)

The only distinction between adulthood and childhood, for what I can see, is that the adults have learned to stare at walls... without drawing on them.

So whilst I am sat here trying to learn economic history arguments, remembering to wash the bed linen, keeping enough in the bank for May's rent, I am really just pretending. Pretending because we got told to pretend; pretending is what adults do best. I'd rather be eating ice cream and uninhibitedly jumping up and down on my bed to S Club 7.