2019 – Major League Baseball announces that it has reached an agreement with the independent Atlantic League to have the circuit test out some potential rule changes this year, including larger bases, moving back the pitcher’s mound by two feet, limiting defensive shifts and imposing a minimum numbers of batters faced a by a relief pitcher brought into the game. All balls and strikes will also be called by an automated system, and not the home plate umpire, except for a few specific exceptions.

On March 8, 2019 — 2019 – Major League Baseball announces that it has reached an agreement with the independent Atlantic League to have the circuit test out some potential rule changes this year, including larger bases, moving back the pitcher’s mound by two feet, limiting defensive shifts and imposing a minimum numbers of batters faced a by a relief pitcher brought into the game. All balls and strikes will also be called by an automated system, and not the home plate umpire, except for a few specific exceptions.

Sources –
Baseball Reference March 8
SABR Games Project
National Pastime March 8
Retro Sheet
Replay The Game