To do this, change your formula to =DATEDIF(A2,TODAY(),” y”). Excel will do the rest by identifying the date and calculating the age. If you really want to get specific, ...

DATEDIF(), which means Date + Dif, is a compatibility function left over from Lotus 1-2-3 that Microsoft adopted in Excel version 2000. It's fallen off current Excel menus, but you can still use it.