Baseball Age (Seasonal Age)

Definition

A player's baseball age indicates how old he is as of June 30 in a given season.

The purpose of baseball age is to establish one age per season for each player, even if a player has a birthday during the season and spends parts of the campaign at two different ages. A given season will often be referred to as a player's "age-x season," with "x" being the player's baseball age. So, for example, if a player turned 25 years old on April 15 in a given year, that season would be his age-25 season. But if another player didn't celebrate his 25th birthday until July 5 that same year, it would be considered his age-24 season.

Note: Baseball age is not an official metric, but it is widely used in baseball literature and media.