1990
You had (or will have) your 10th birthday in 2012.
If you have had your birthday this year, you would be 63. If you have not had a birthday this year, you would be 62.
On your birthday in 2012, you would turn 15.
Before your birthday in 2012, you're 19. On your birthday in 2012, you turn 20.
You would be 21 years old on your birthday.
In 2012, you would have been born in 1990 if you have had your birthday this year. 1989 if you are 22 and haven't had a birthday yet this year.
You would celebrate your 35th birthday this year (2012)
You would have celebrated your 55th birthday this year (2012)
They would celebrate their 17th birthday this year (2012)
You would celebrate your 27th birthday this year (2012)
32 for most of the year and 33 after your birthday in December 2012.
You would have celebrated your 38th birthday sometime this year (2012)