It's laughably ridiculous, the concept behind the romantic comedy-drama One Day, so maybe there's no logical way to defend the fact that the film charmed me. It simply does much of what you ask of a romance: gives you two interesting people and a reason to hope they wind up happy.
The story begins on July 15, 1988, when a bunch of Brits are celebrating their college graduation. Among them are Emma Morley (Anne Hathaway) and Dex Mayhew (Jim Sturgess), who take the opportunity for a casual hookup - almost. They resolve to remain friends, and over more than 20 years, we revisit them every July 15 to see how that friendship is working out.
Naturally there are a variety of impediments. Often they're in different countries; Emma begins a long-term relationship; Dex gets married; Dex becomes a popular TV personality who hosts vapid variety shows, becoming an alcoholic, addict and general dickhead in the process.
Yet somehow their worlds almost always manage to intersect on St. Swithin's day. July 15 marks not only the day their friendship first blossoms, but also a day for weddings, having critical fights, confessing mutual feelings and...well, a few other significant things. While some of the events could realistically be attributed to the sentimental resonance of the date, it is a gimmick.
But One Day works for that most fundamental of reasons: affection for the characters. Anne Hathaway continues to emerge as a genuine acting force, allowing Emma's growing self-confidence to permeate every interaction. And while Dex muddles through a stretch of obnoxiousness, Sturgess finds something basically decent in his desire to maintain the friendship. The tone is light and frisky throughout much of the first hour, allowing the charming chemistry to build so that the story's more serious turns don't feel exploitative.
One Day may save its smartest decision for last, as the narrative reverses course to show us the day after July 15, 1988. Not only does it showcase the characters at their most endearing and vulnerable, but it escapes the gimmick enough to show us that all the other days between Emma and Dex were just as important. That's the way you get a cynical, arms-folded critic to suspend disbelief: build a relationship strong enough that I start to care about those other days.