One Day, Lone Scherfig, 108 mins, (12A)Conan the Barbarian, Marcus Nispel, 112 mins (15)

The surprisingly enervating film of David Nicholls' hit novel may win you over in the end, but it would have been better as a four-hour TV mini-series

Just in case you're one of the seven people in the country who haven't read One Day, David Nicholls' hit novel tracks the lives of two mostly platonic friends, Emma and Dexter, over 20 years.

It begins when they nearly sleep together the morning after their graduation from Edinburgh University, and it checks in on them on the same date – 15 July – of every successive year, as we wait to see if they're ever going to put us out of our misery and become a couple.

Now, considering that novels tend to be divided into chapters, and that they take a while to read, they're the ideal form for a story with such an episodic structure and protracted time span. But considering that films aren't divided into chapters, and are usually over and done with in less than two hours, you can see immediately why a film of One Day might have problems. More than anything, it reminded me of those "Previously on ..." montages which open the later episodes of TV drama serials.

In order to fit in a taster of what Emma and Dexter are up to every year, the screenplay, also written by Nicholls, can't give us anything except a brief scene establishing where they're living and working – and then it's time to jump forward another 12 months.

We see Emma (a wobbly-accented Anne Hathaway) settling into a waitressing job in a Mexican restaurant, and Dexter (an uncomfortable Jim Sturgess) drifting in and out of a late-night TV career. But we don't get to see them hanging out together, or opening up about their feelings, so we never know why they persist in viewing themselves as friends, despite all evidence to the contrary.

The irony is that Nicholls' background as a television dramatist shines through the novel's comic set pieces, and yet these set pieces – the most visual, cinematic parts of the book – keep falling by the wayside in the film's dash through the decades. And without them, One Day is fundamentally the depressing story of a man who's ruining his life.

For a film that covers 20 years so hastily, it's odd how enervated One Day is. But, eventually, the pervasive gloominess does serve some purpose. As Sturgess's hair gets greyer and greyer, the film – while a failure as a will-they-won't-they romance – becomes quite effective as a meditation on what it's like to grow old, tired and disillusioned.

It must be effective, because by the closing stretches, the viewer is feeling pretty old, tired and disillusioned, too. And then, once One Day has worn its audience down, it arrives at a 10-minute sequence of Emma and Dexter enjoying each other's company, and at last the fact that they've been fending each other off for so long starts to seem poignant rather than perverse. By the very end, then, One Day had won me over. But a four-hour TV mini-series would have been better. They've got all the "Previously on ..." montages in the can already.

Conan the Barbarian is the kind of film which just makes you feel sorry for everyone involved. After all, a swords'n'sorcery saga takes a lot of work, and I found myself fretting about all the hours Jason Momoa must have spent in the gym to get those muscles, all the expense that must gone into the ridiculous costumes and sets, all that effort that must gone into lugging lights and cameras to the Bulgarian hills and caves where the film was shot ... all to make such a noisy, bombastic load of nonsense.

Bearing only a passing resemblance to Robert E Howard's 1930s stories, the plot has something to do with a necromancer's video-game quest for the shards of a mystical mask, and Conan's quest to twirl his sword around like a majorette while shouting "Yarrghh!". But I wouldn't worry too much about the whys and wherefores: when a film has an entire mountain collapsing for no reason, it's obvious that the script wasn't a priority.

The 3D, by the way, is the lousiest since Clash of the Titans.

Next Week:

Nicholas Barber sees Fright Night, with David Tennant in his long-awaited first major film role, starring alongside Colin Farrell

Film Choice

Brendan Gleeson puts a vigorous Irish spin on the bad-cop thriller, in John Michael McDonagh's uproarious, juicily written comedy The Guard. And a touch of vintage English cynicism comes courtesy of Alec Guinness, Dennis Price and director Robert Hamer, in Ealing's enduring satire Kind Hearts and Coronets, now re-released.

Also Showing: 28/08/2011

Powder (100 mins, 15)

One of the year's most amateurish films, Powder is an incoherent Britflick featuring a morose indie singer who stands around in an almost catatonic trance while irritating hangers-on declare that he's a genius. Never have sex and drugs and rock'n'roll seemed so dull.

R: Hit First, Hit Hardest (99 mins, 18)

This low-key Danish prison drama is convincingly grim, but is the same old story of a laconic youth struggling to survive by doing what Mr Big tells him. It pales into insignificance next to last year's A Prophet. Incidentally, in Denmark it was just called R. The dopey subtitle was added for the international market, presumably to fool us into thinking it might be a Jason Statham movie.

Final Destination 5 (90 mins, 15)

The most repetitive of horror franchises is back again: each new episode brings so few twists to the ghoulish formula that it's less of a sequel than a remake of the first one. But FD5 is fine if you're in the mood for some humour that's both tongue-in-cheek and iron-spike-through-face, and at least the use of 3D makes sense when this many sharp implements are being hurled at the viewer.