Little League adopted a rule change starting in 2016 that changed the date of birth for a player from April 30 to August 31. While Little League adopted the rule early, other Leagues have followed suit. Starting in 2018 PONY baseball will implement the change. However, Cal Ripken, Babe Ruth, USSSA, and AABC will not make the age change.
The birthday age cutoff is important to know, notably since 2018 marks the start of the required USA Baseball stamp bats. JustBats.com has provided some resources to help if you have questions regarding the cutoff age dates.