We tend to discuss decades as though they were mysteriously discrete socio-cultural units, rather than artificially designated spans within a ceaseless flow. References to “the 1930s”, “the 1960s”, “the 1980s” stir instant associations regarding fashion, attitudes and political temperature. Yet it’s odd how long it can take for a consensus of such shared impressions to develop. Eight years after they ended, the 90s remain ill-defined. Perhaps what it takes is for a generation that doesn’t quite remember the period in question to reach maturity. Lacking a memory of it, they feel left out; they reclaim it, romanticise it. (Look at all those twenty-something club kids currently reviving the vilest excesses of 80s fashion!)

The young stars of The Wackness, Olivia Thirlby, Josh Peck and Mary-Kate Olsen, were all born in 1986. For them and their fanbase (Peck and Olsen are erstwhile child stars who have been famous for much of their short lives), the stylistic trappings of this film – “daisy age” hip hop, graffiti fonts, baggy striped t-shirts, floral sundresses worn over t-shirts – come from an exotic past. Writer/director Jonathan Levine, meanwhile, graduated high school in 1994, the year in which the film is set, and describes it as “semi-autobiographical”. His contemporaries are grown-up cultural players now – so expect The Wackness to be just the start of the nostalgic 1990s theme party.

Peck plays Luke, an introspective, sweet kid whose sole claim on the respect of his peers is his weed-dealing business. One unlikely customer is his shrink, Squires (a brilliant, manic Sir Ben Kingsley), who accepts herb in lieu of his fee. Over one troubled summer, Squires succumbs to a full-scale – and hilarious – mid-life crisis, while Luke falls hard for Squires’ beautiful stepdaughter Stephanie (Thirlby). Levine’s film captures the joys and agonies of growing up (at any age) with infectious warmth, wit and passion. Think Ferris Bueller with a fat spliff in his hand and a floppy fringe in his eyes.