According to the IRS, what is your age? (IRA contribution)

The amount you can contribute to your IRA changes when you are 50. So what is your limit the year you turn 50? Lets say you turn 50 on September 2nd, is your limit that year?
$6000 since you started the year at age 49?
$6250 prorated that you turned 50 at the start of the 4th quarter?
$7000 since you ended the year at age 50?

From this site

(bolding mine)