"I honestly believe it would have all gone wrong and he'd have cheated on her, if they got together a day earlier," concurs Anne Hathaway, who stars as Emma.
"Also, she wouldn't have stood up to him or been able to be her own person, right up to when they get together."
Consequently, One Day suggests that the course of true love isn't always as simple or smooth as it could be, as Emma and Dexter flit from one calamitous relationship to the next - until they finally surrender to 20 years of suppressed passion.
"I think the 'will they, won't they' get-together aspect of One Day is definitely one of its attractions," says Sturgess. "That's what makes it frustrating to watch from the outside, because everyone else knows they should be together - that the perfect woman for him is right under his nose. But I think Dexter needs to experience all the trials and tribulations he goes through to finally come to that realisation."
When Dexter and Emma eventually end up together, the repercussions are both unexpected and unsettling, which strengthens the suggestion that time is precious and love is fragile.
"That's so true," acknowledges Hathaway. "If the movie encourages us to try to do one thing, it's not to take our lives for granted. But you also have to be realistic and honest about who you are and what's right or wrong for you at any given time in your life. I think that's the crux of this story, and something it manages to convey in a very clever way."
Hathaway admits that it was the dilemmas One Day posed and the myriad twists and turns of its plot which captivated her and convinced her to pursue the part.
"When I finished reading the script I felt like I was coming up for air because I was so moved by it," she says. "I immediately thought that if there was any chance that I could be a part of bringing this film to the big screen, then I'd be so honoured to do that.
"Very few things I read transport me like that, which is why I asked if I could meet with Lone. I even sent her a tape with a bunch of songs I thought Emma would be into," recalls Hathaway, blushing at the memory. "I wanted to try and give her the feeling that I understood Emma and convince her that I was the right person to play her. Luckily, she seemed to respond to that."
For Sturgess, the appeal of playing Dexter, a fun-loving womaniser and TV presenter of a music show was equally intoxicating, albeit for different reasons.
"I've been in bands since I was 15 and music has been my main passion for as long as I can remember," he smiles. "So, to make a film that starts in 1988, when fantastic bands like the Stone Roses and the Happy Mondays were emerging from the whole Manchester scene was great. It was funny, too, because me and Anne swapped loads of 80s music and she ended up listening to all these English bands she'd never even heard of before."
However, playing Dexter wasn't as much fun as he imagined. Partly that's because the role was more challenging and nuanced than he'd anticipated.
"I thought it would be easy to play him, because he's a fun-loving guy, who lives life to the full," he shrugs. "I just thought it would a great laugh, being in London in summer, and playing this outrageous character. But it ended up being a lot more complicated and traumatic than I bargained for, because he goes through so much - there's a lot of pain there.
"I don't know why I didn't take that into account," laughs Sturgess, ruefully. "It actually ended up being quite an intense ride for both of us because it was a very complicated film to make, with all the jumping around from one time of their life to another. One minute you might be playing a 37-year-old with a child and then you go off to lunch, come back and you're playing a 23-year-old cocaine-sniffing, TV presenter. Those time shifts meant we had to be completely on top of where we were at, as Emma and Dexter, and also with what was going on between them."
"It was hard for me too," confesses Hathaway. "There are a lot of fans of this book, who are very possessive of Emma. Also, as an American playing a Brit, it was a real challenge with the accent, understanding the culture and mastering her dry sense of humour. Not that I'm complaining because I realise just how lucky I am to not only be working, but to also be playing such a wonderful character.
"I'm constantly reminded just how lucky I am to be doing exactly what it is that I want to do, because there are plenty of people who don't," she concedes. "But the way my career's gone has all been a lot of happenstance. That's all it is. There's no master plan. I just figure out the best part, best project and best director out there and try to be in that experience.
"Realising that luck has a lot to do with it means you don't take anything for granted. It ensures you turn over every stone and prepare yourself as best as you can. That's what I did with One Day," she asserts. "I can guarantee you that I worked my ass off for this, no matter what people may think about me as Emma. You know, at the end of the day there's a certain satisfaction in knowing that you've done your damnedest."
LOWDOWN
Who: Anne Hathaway and Jim Sturgess
What: One Day, the film of the David Nicholls' best seller
When: Opens October 27
-TimeOut
