Age based on a certain date

I need to be able to calculate someone's age on a certain defined date. My use case is for youth sports where the age of a participate for that season (league age) is defined as the age of the participant on a certain date. For example, Little League Baseball determines the league age of a participant by the actual age on August 31st of the current year. So a child born on 09/01/2020 will be 5 for the 2026 season while a child born on 08/31/2020 will be 6 for the current season.