On January 1st 2009, you say "Two days ago I was 28, but next year I will be 31"
- two days ago was Dec 30 2008 and you were still 28.
- the next day, Dec 31 2008 was your birthday so you turned 29.
- This year (in 2009), you will turn 30 - so when you say "I'll turn 31 next year" on January...