The Age Determination Date for a Little League Baseball player is the actual age of a child as of August 31 of the current year. (Note: The Age Determination Date for a Little League Softball player is the actual age of a child as of January 1 of the current year.) These respective dates identify the “league age” as it relates to a player’s eligibility to participate in any of Little League’s divisions of play.
For example, if your Little League Baseball player was born on 7/1/2011, he is considered to be "League Age 10" for the Spring 2021 season.
See this
age calculator on the official Little League website for additional assistance in determining league age of your child.