"Today Rebel Wilson celebrated her 29th birthday for the fifth time. And I totally get why."

Have you ever been tempted to lie about your age?  If yes, you are in some very good company.

Aussie actress Rebel Wilson has just turned 29. Apparently.

I say ‘apparently’, not because I think she looks or acts any older or younger than that but because the world seems confused about Rebel’s exact age.

When Rebel spoke to Lisa Pryor for this article in the Sydney Morning Herald back in 2002, she was 22.

Rebel Wilson was 19 by the time she first saw a professionally produced play. In the three short years since that formative experience, she has written two plays of her own, starred in a feature film and started her own production company.

But when she spoke to the same publication two weeks ago, she was only 28.

She was also 28 when she spoke to The Age in 2008.

Now, I’m pretty bad at maths, but I know that’s not quite right. Also, Twitter is awash with rumours like this:

Pretty sure Rebel Wilson is lying about her age. I’m also 27 & knew her when I was 13. She was at uni studying law then.

— Natasha Lee (@tashlee) October 8, 2013

But before you get upset about me picking on Rebel, or suggest I’m calling one of our most successful comedy exports a liar, I’m not.

It is perfectly possible that the journalists writing these stories misunderstood or misreported Rebel’s birthdate (Feb 3, 1986, according to Wikipedia, IMDB and biography.com,people).

I am not here to tell you definitively that Rebel Wilson is lying about her age. That is entirely her business, and I’m a huge admirer of what she has achieved, so really, she could be 102 and it wouldn’t matter.

Here is Rebel being fabulous at many ages (post continues after gallery):

But I am here to tell you that I absolutely understand why, in this supposed age of honesty, confession and declarations that “40 is the new 30”, a smart and talented woman might just find herself tempted to do exactly that.

If I could lie about my age, I would. I can’t, because if I lie about anything much, I go red to my temples and start to stutter. I was not born with a poker face. But I have reached a number where I hate telling people how old I am, and if I can possibly avoid it, I do.

Of course, I know that lying about your age is  a ridiculous affectation, a gross vanity and an insult to those robbed of the chance to grow old.

Of course, I know that any shame about ageing is shallow, entirely foolish and something to be conquered.

But I can’t help it – I’m trying to shake it off, but age matters. It doesn’t matter to the people who know and love you, but it matters to the outside world.

Think about it. Think about the assumptions you make about, let’s say, a 40-year-old woman, as opposed to a 20-year-old one. Think about what you imagine she looks like, what she will have achieved in her life, what kind of home life she might have, what kind of job she might want, what kind of money she might have in the bank.

Which one of those women do you imagine will be more enthusiastic, more energetic, more athletic, more ambitious?

Which one do you think would be more motherly, more established, more settled, more serene?

Rebel Wilson rocked a $66 Asos dress on the red carpet last night.

Like it or not, we are all still playing in a world where status is bestowed on the young and the beautiful. Especially if you are a woman. And especially if you are an artist, like Rebel.

It’s true that Rebel doesn’t play in the “hot girl” space that most young actresses are forced to inhabit. But still, when she was on the brink of a Hollywood career, launching herself into one of the most competitive markets in the world, it would have made sense for an agent to have ensured she could play a college student, a feasible flatmate and a hapless shopgirl. Chipping a few years off your age makes sense. Because no-one’s rooting for a 34-year-old freshman.

Rebel at her comedic best as Fat Amy in Pitch Perfect (post continues after video):

The 20-something women that I work with are in an enormous hurry to achieve everything before they’re 30 – a glittering career, a wedding, a baby, a house. Why? Life doesn’t stop when you’re 30. If you’re lucky and wise, you will live for many, many more years, achieve many more things, have many more adventures, make many more mistakes.

But these smart women know that perception changes at 30. You’re no longer the Bright Young Thing, the over-achiever who ticked off their to-do list at break-neck speed. And – I suspect – Rebel Wilson knows that, too. Which is why she’s been at that magical age of 28 for so long. Old enough to be taken seriously, young enough to be New.

And we all love New.

This is why 28 is good. All these women are there. (Post continues after gallery)

It isn’t until you cross the badlands of your 30s that you realise how much the world is geared towards the young. How their voices shout the loudest, how big business is endlessly pitching for the dollars that have not already been spent on the mortage, the childcare, the people mover. How the media world is now entirely fashioned around their short attention spans and their obsession with immediacy (okay, in that regard, I am young at heart, the 90s were interminably slow).

Yes, I know that the serious power rests in the hands of the older generations. World leaders are still overwhelmingly, depressingly, grey-haired men. But for many people who fall into neither camp, they find themselves anxious that they are ageing into irrelevance. That prospective lovers will find them saggy and unappealing and that prospective employers will find them too expensive and demanding.

So yes, I understand why women lie about their age.

But here’s my suggestion to myself, and everyone else: Don’t.

Because shame about our number is just another form of shame that holds us back. The world needs to see that women of all ages can achieve, create, be bold and brave and fabulous. That energy and possibility and promise are not the preserve of the under-30s.

We need to own our number.

And here’s mine, Rebel:  Last month, I turned 43.

If you want to commiserate with Holly about her number on Facebook, come be her Friend.