2018 – Minor League Baseball announces some changes to the rules that will be used throughout the minor leagues starting this season. First, there will be a limit of six mound visits per game in AAA, similar to the rule change just introduced in Major League Baseball; lower classifications will allow more visits: 8 in AA and 10 in Class A. A 15-second pitch clock will be introduced with the bases empty, and 20 seconds with men on base. Finally, a variation of the Schiller Rule will be used beginning in the 10th inning, as each half inning will start with the batter preceding the first batter of the inning already on second base. That last rule was already in use in some Rookie-class leagues.

On March 14, 2018 — 2018 – Minor League Baseball announces some changes to the rules that will be used throughout the minor leagues starting this season. First, there will be a limit of six mound visits per game in AAA, similar to the rule change just introduced in Major League Baseball; lower classifications will allow more visits: 8 in AA and 10 in Class A. A 15-second pitch clock will be introduced with the bases empty, and 20 seconds with men on base. Finally, a variation of the Schiller Rule will be used beginning in the 10th inning, as each half inning will start with the batter preceding the first batter of the inning already on second base. That last rule was already in use in some Rookie-class leagues.

Sources –
Baseball Reference March 14
SABR Games Project
National Pastime March 14
Retro Sheet
Replay The Game