Amanda and Leo are born in the same hospital on the same day. Every year they celebrate their birthday together. Until their 10th birthday. Amanda overhears Leo saying something about her that causes her to walk out of their party and not talk to him for a year.
When their 11th birthday arrives they wake up as usual and start their routine as usual. Each has planned a separate party for themselves. Neither is happy without the other. Most of Amanda’s guests leave to go to Leo’s party. Amanda goes to bed without opening her gifts.
When her alarm goes off the next morning she is confused. Not remembering why she would set her alarm on a Saturday. When her family starts to wish her “happy birthday” she believes that they are pulling a prank on her. But she soon realizes that she is back to the day of her birthday again! Everything is the exact same as it was on her original 11th birthday. Afraid that she is going crazy she goes through the day doing exactly what she did originally. Once again she is woken up by her alarm only to start her birthday day all over again. This happens several “days” in a row. Leo realizes that they are both re-living their birthday first.
Once they realize that they are both reliving their birthday they set out to try and find out how to make it stop. They learn about an old family feud between great grandfathers. They take a day to do whatever they want to do. They do nice things for people hoping that that will break the spell. They become best friends once more.