On New Year’s Eve, Teddy [Rafe Spall] races to kiss his girlfriend Becka [Dena Kaplan] by midnight. By mistake, he kisses another woman named Leanne [Zahra Newman], who is wearing the same dress. Leanne helps Teddy when he goes into anaphylactic shock after inadvertently swallowing a peanut that was in Leanne’s mouth, and the two begin a relationship.
A few years later, Teddy and Leanne visit Teddy’s father’s grave to share the news that Teddy has proposed using the ring he personally crafted for Teddy’s mother, though they haven’t set a date. A strange woman overhears them and cautions Teddy against wasting his life, offering a wedding gift in the form of a tin can and instructing him not to open it until his tenth anniversary, the year traditionally associated with tin.
The morning after the wedding, Teddy wakes to discover that exactly one year has passed and Leanne is 18 weeks pregnant. A few minutes later, time shifts to their second anniversary, and he is the father of a baby girl who, to his shock, is named Talullah. Teddy realizes that time is moving forward for everyone else while he seems to be stuck, and he asks his best friend Sam [Ronny Chieng] to meet him in one year with an anniversary present, which he does. They theorize that Teddy’s predicament is similar to that in Groundhog Day, and that Teddy must have a “perfect day” to break the cycle.
In the intervening year, Teddy and Leanne begin couples’ counselling, and their therapist asks them to write letters to each other. Leanne feels that Teddy isn’t the man she married, as he spends all his time at work. Teddy promises he can change, but the letter he wrote betrays the resentment he feels at being forced to be the family breadwinner instead of pursuing his dream of photography, while Leanne chases a “pipe dream” of being a writer.
On Teddy and Leanne’s fourth anniversary, Teddy is shocked to find Leanne gone; they have agreed to a trial separation. Worse, Sam has been diagnosed with skin cancer, and Teddy is shaken by his weight and hair loss. On their fifth anniversary, Teddy wakes up from a night with his ex Becka, whose marriage has also fallen apart and who Teddy has been seeing casually for a few months. Becka vows to stop seeing Teddy, but they are still together a year later. Teddy wonders what keeps drawing them back together when they’re clearly wrong for each other, and Becka notes that she would have saved her marriage if she’d known then what she knows now.
Teddy visits Leanne and learns that she is the owner of a Great Dane puppy (a dog Teddy disliked) and is dating a man named Patrick [Josh Lawson]. He suggests they get a kiddie pool, and as time shifts again, he falls into it. Leanne and Patrick help him out, and Teddy is shocked to see Leanne is no longer wearing his ring. She shamefully admits that she lost it at the beach and couldn’t find it despite hours of searching. Teddy takes the dog for a walk to the beach, where another year passes. He finds a chocolate bar containing peanuts in the sand and contemplates suicide, until his daughter Tallulah, now seven, tries to cheer him up.
Another year passes. Teddy tries to call Sam, only to learn that Sam has died. He visits Sam’s grave, where he encounters again the strange woman who gave him the “gift” of fast-forwarding his life. The woman explains that she, too, was given a similar gift before her own wedding; her experience helped her realize she didn’t love her fiancé and was, in fact, a lesbian. She often visits her lover’s grave to show how she uses the extra years she never got to give to others.
On their tenth anniversary, Teddy rushes to Leanne’s house and asks her to find the old tin can. When she opens it, Leanne miraculously finds Teddy’s father’s ring. Teddy and Leanne finally reunite, and Teddy wakes up the day after the wedding. Now with a renewed outlook on life, Teddy calls his boss to say he will cut down his hours and study photography, urges Sam to get screened for skin cancer, and resolves to give the tin can to Becka so she can save her own marriage.
