They say nostalgia ain't what it used to be, but try telling that to anyone who has been to a gig, a bar, or out of the house at all during this long hot summer of looking back. 2009 is the year of re-living lost youth, it turns out.
I am in a position to say this confidently since I now have a GP who is younger than me and am suddenly seeing the fashions of my youth recycled by the young.
I went to a party in the area known as London's Trendy Hoxton last weekend and thought I had accidentally walked into an Eighties theme night, but I was kindly informed that it is now very witty to dress like The Kids From Fame's less imaginative younger siblings and that I should rip my jeans and get with the programme.
Those who set the bill for last weekend's Grandads' Glastonbury were maybe responsible for kicking off the latest wave of nostalgia chic, holding up Bruce Springsteen, Neil Young and Blur before Somerset's baffled youth. But they weren't the first festival veterans to look back.
Next month sees the long-planned publication of two books on the 40th anniversary of Woodstock – one of them is a limited edition called Woodstock Experience and is signed by none other than Arlo Guthrie (ask your dad).
The weather, too, is provoking déjà vu all over southern England. Yesterday, my neighbours asked me to water their plants while they were on holiday, in a spirit of solidarity that hasn't been witnessed in London since 1976 when it was last this hot, I was just born and everyone else was saving water by bathing with a friend.
And then Michael Jackson's death sparked a wave of nostalgia that sent all of his songs hurtling back up the charts, and was also reminiscent of the passing of that other patron saint of the eating disorder, Princess Diana.
Where were you when you heard that Jacko died? I happened to be on a petrol station forecourt when a weeping man wound down his car window to shout out the news. How suburban. How Seventies.
When we come to look back fondly on the great retro-fest of the late Noughties, however, the one thing that will symbolise the era is band reunions. The Police, Crowded House, Duran Duran, Boyzone, Spandau Ballet, The Spice Girls... I must have been pretty on trend on Wednesday night when I caught the slow train to Wembley to see Take That in concert.
The last gig I saw at (the old) Wembley stadium was, as it happens, Michael Jackson. Going back there is a reminder of how incomparably depressing is the modern 02 arena, which charges £4.30 for a pint of lager and won't let you keep the cap on a bottle of pop "in case you use it as a missile".
Seeing 160,000 hands waving in unison as 80,000 thirtysomething women sweat with excitement is quite something at Wembley. Watching the old dance routines redesigned for a band of grown up men is weirdly moving. Noting that little Mark Owen is still hot at 37 is quite cheering. But finding a Wembley security guard, a burger chef and a refuse collector dancing outside the toilets to "Re-light My Fire", that is pure nostalgia. Long may it come back again – and again.