Q: I was 29 the day before yesterday and next year I will be 32. This is true only one day in a year. What day is my birthday?
A: December 31st is the birthday so on December 30: age = 29
Dec 31: turns 30
Jan 1 : the day it is ‘now’ in the question
will turn 31 at the end of the current year (it is far away as it is Jan 1 and the birthday is Dec 31)
therefore the person will be 32 at the end of the next calendar year