If someone has had a birthday already this year then you get their age by subtracting their birth year from 2009. If some has not yet had a birthday this year (which is your case) then you subtract 1 from the answer. So in your case 2009 -1988 = 21 ,but you didn't have a birthday yet so you must subtract 1 to get 21 - 1 = 20. Sorry, but you're still legally only 20, until September.
You would have just turned 23.
Arrelious Benn was born on September 8, 1988.
Caitlin Hill was born on September 8, 1988.
Chantal Jones was born on September 8, 1988.
Curran Jacobs was born on September 8, 1988.
Gustav was Born on September 8, 1988 in Magdebrug Germany
Arrelious Benn was born on September 8, 1988.
Caitlin Hill was born on September 8, 1988.
Chantal Jones was born on September 8, 1988.
Arrelious Benn is 23 years old (birthdate: September 8, 1988).
Caitlin Hill is 23 years old (birthdate: September 8, 1988).
Chantal Jones is 28 years old (birthdate: September 8, 1988).
Gustav Schäfer is 23 years old (birthdate: September 8, 1988).