That is why the explanation continues: "(other than pedantic exceptions due to calendar issues or timezone alterations, or someone dying before their birthday, or being born on a leap day, none of which apply in this case)".

A friend of mine has his birthday on feb 29th. He was turning 49 and me and my gf showed up to his party with balloons with the number 12 on them (since that's how many actual birthdays he'd had).