Logic question?

Jenny is 17 years old, next year she'll be 20 years old, how is this scenario possible?
Update: if no one solves this by tomorrow I'll post the answer in a new update, though there is some smart posters here, so we'll see.
Update 2: I phrased the question wrong, sorry all, I will re-ask the question the correct way and give everyone a new day to solve it: "The day before yesterday Jenny was 17 years old, next year she'll be 20 years old, how is this scenario possible?" BTW, couple ppl mentioned leap years, no, that has nothing to... show more I phrased the question wrong, sorry all, I will re-ask the question the correct way and give everyone a new day to solve it: "The day before yesterday Jenny was 17 years old, next year she'll be 20 years old, how is this scenario possible?" BTW, couple ppl mentioned leap years, no, that has nothing to do with this.
Update 3: the answer: the scenario can be true if it's January 1st and Jenny's 18th birthday is on December 31st, hence she was 17 the day before that (dec. 30th) and her 19th birthday comes the current year, meaning her 20th birthday comes next year, this was a tough one to sorta explain but if you read carefully it... show more the answer: the scenario can be true if it's January 1st and Jenny's 18th birthday is on December 31st, hence she was 17 the day before that (dec. 30th) and her 19th birthday comes the current year, meaning her 20th birthday comes next year, this was a tough one to sorta explain but if you read carefully it all really checks out.