I look at it from a formal/legal perspective. By many definitions, the person will not be considered to be a year older on February 28th. (E.g. in the U.S., t

I look at it from a formal/legal perspective. By many definitions, the person will not be considered to be a year older on February 28th. (E.g. in the U.S., they can't have a drivers' license yet if they are 15 years old and their birthday is February 29th., nor can they drink if they are 20 years old.) They will be considered to be a year older on March 1st. Going on that, I view the birthday to, descriptively, have shifted a day later. And calendar-wise, that actual day that would in a leap year be counted as February 29th is instead counted as March 1st.