Twenty one years? Twenty one bloody years? That's the length of time it takes to have a kid, send it to school, watch it grow up and then kick it out of your house. It is a very long time.
Yet the much-hyped sequel to Trainspotting, the less-than-imaginatively titled T2: Trainspotting, somehow manages to make its predecessor feel both very recent and remarkably dated.
Is it really two decades since Danny Boyle took Irvine Welsh's cult novel and hurled it at the screen?
Like most people in their early 20s when Trainspotting first appeared like a film that had not so much been released as it had escaped, I have fond memories of both the flick and the times. In fact, you could argue, as people my age have an unfortunate habit of doing, that we really never had it as good as we did in the 1990s. Sure, there was the brief, illusory period in the 2000s when almost everyone had access to cheap mortgages and a bit more money in our pockets.
But even the so-called boom years involved working 12-hour shifts, saw massive increases in social anxiety and stress levels, and while we may have been earning better money, the key is in the word 'earning.
The era of Trainspotting was different, though. This was the rise of the New Lad, the elevation of footballers into household names, the chart wars between Oasis and Blur, all carried by a wave of optimism and hedonism. It was also an era of rejection - rejection of every staid middle-class life goal.
That's why Renton's speech carried so much weight: "Choose a job. Choose a career. Choose a family. Choose a f***ing big television. Choose washing machines, cars, compact disc players and electric can openers...Choose life," before he concluded: "But why would I want to do a thing like that? I chose not to choose life: I chose something else. And the reasons? There are no reasons. Who needs reasons when you've got heroin?"
Now, two decades on from when we last saw Renton sneak out of a London hotel room while his mates slept, stealing the £16,000 they had earned on a skag deal, there is the legitimate question - does the world really need to see what has become of Renton, Spud, Sick Boy and the always-terrifying Begbie?
Maybe. Maybe not.
But it's a testament to the director that I spent much of the film being hit by wave after wave of flashbacks revived by the snippets of music we'd heard in the first instalment - 'Lust For Life', a new mix of the immediately recognisable 'Born Slippy' by Underworld. If the people who came of age in the 1990s were, as the Prodigy claimed, the jilted generation, they seem to have become the nostalgic generation.
There's also something rather sad about people who have yet to hit middle-age getting all misty-eyed over their relatively recent youth. As Sick Boy sneers to the prodigal Renton: "Nostalgia, that's why you're here. You're a tourist in your own youth."
It's a nod to the viewer - Danny Boyle knows we want to go back. The question is whether we should bother.
So, Renton has come back from Amsterdam, eager to make amends with his best mate Sick Boy, who has become a seedy, coked-up blackmailer, lost in a morass of depravity. Although, another little reference back to Renton's original speech, Sick Boy does indeed have a f***ing big television, one which features the video for the Rubberbandits' brilliant 'Dad's Best Friend'.
Rather like the other stand out movie from that time, Fight Club, Trainspotting was about male alienation and the often primal attraction to violence.
Watching the older, if not necessarily wiser, characters return once again brought Fight Club to mind.
Because while Tyler Durden was two personalities in one body, Renton, Sick Boy, Spud and Begbie could all be constituent parts of the same personality - the more sensible Renton being the ego, Sick Boy the super ego with Begbie a terrifying glimpse into the snarling face of the unleashed id.
One thing is for sure, though. As much as we all like to poke fun at millennials and their fussy, often joyless ways, I'm glad to have been a 24-year-old watching the first movie when it came out, than a 24-year-old today watching the sequel.
They say you should never go back, and T2: Trainspotting, as impressive as it undoubtedly is, reminds us why that's true.
Frankly, on leaving the cinema, I was struck by one thought - I'm too young to feel this old...