I believe I misplaced these credentials somewhere between getting my belly button pierced and ruling out any movie that starts after 6:30pm because I will fall asleep.

I thought there was merely a blink between those two things but it seems years have passed. And lately, there have been a few key moments when the realisation that I’m no longer a kid has startled me stupid.

Perhaps some will sound familiar to you.

Like working out you’ve been out of school longer than you were in it. Or being gob-smacked to consider there are people driving cars and having sex who were born in the nineties. The NINETIES. Or taking your child to an appointment with a doctor who is younger than you. How did that happen? When did doctors and police and even politicians get so young? Was I napping? Because they used to be old people and suddenly they’re not.

It’s funny though, how your definition of old changes as you get, well, older. I’ve been to a handful of 40th birthday parties this year and sometimes, it’s a shock to look around the room and see so many bald heads. Nothing wrong with bald but it doesn’t exactly shout 22, does it?

Back in 1982 when Prince sang “tonight we’re going to party like it’s 1999”, I remember doing some basic arithmetic. Even though 1999 seemed inconceivably far into the future, I deduced that I’d be 29 years old on that particular New Year’s Eve. Emphasis on the old. “Oh what’s the point of a party,” I thought at the time. “By 1999 I’ll be a sad old loser who won’t be remotely interested in any type of fun. At midnight I’ll probably be home asleep after drinking a cup of herbal tea”

Oh wait, I just described my New Year’s Eve 2008. Turns out I was off by less than a decade.

I also seem to have reached the age where your children laugh at you when you try to use certain words. Young words. For shizzle. When I said that to my tween son a few weeks ago, his eyes nearly rolled out of his head. “Mum, it’s really pathetic when old people try to talk young.” He’s right about that although I couldn’t help protesting, “Look, I used to be cool, you know! I did!” Pathetic is right.

Still, I did feel a little bit hip when I retold the story to two girlfriends who looked at me blankly. “Um, what does ‘for shizzle’ mean?” one finally asked. “Oh phew” said the other. “I thought it was just me. I have no idea either. Never heard of it.”

It was a struggle to keep the cool smugness out of my voice as I explained that it derived from Snoop Doggy Dog and was slang for ‘for sure’. In truth, I’m not actually certain of this and I’m sure there are people already running to their laptops to email me a scathing correction, which I really look forward to reading. No, really.

I know you’re only as old as you feel (or, as sleazy men like to guffaw, ‘you’re only as old as the woman you feel’) and sometimes the disconnect between your actual age and your internal one can be jarring.

A girlfriend was jarred in such a way earlier this year when she attended her nephew’s high school footy game. “I was walking through the crowd and found myself inadvertently checking out a few of the older boys and thinking ‘Oh, you’re a bit hot’ and then realising that I’m twenty years older then them and possibly technically a criminal for even having such thoughts. In my head, I was a high school girl again but they were probably going ‘Sad nanna.’

Then there are times when the generation gap leaps out of nowhere to smack you over the head. Like a few months ago when I was invited by a record company mate to see a showcase by a new Aussie band called Will & Dash who are two 20-year-old girls who write all their own music and just released their first album.

I took a girlfriend with me and as we waited at the bar for our wine, I launched into a detailed moan about how the baby wasn’t sleeping through the night because he was teething. Is that not what people in nightclubs discuss?

Anyway, the showcase was great and afterwards, I met the girls. “I don’t go to clubs much anymore,” I told them, “so I was quite chuffed that I’d pulled together a suitable look until I got into the car and discovered I had Fuzzy Felt in my hair”. They both looked at me blankly. “You know, Fuzzy Felt!” I repeated.

Blankety blank. That’s when I remembered they were 20 and had no clue what I was talking about. Try to explain what a Fuzzy Felt is. Go on. Try. It’s challenging, even when you’re not in a noisy nightclub.

For shizzle.

Can you relate? Had any nanna moments lately?