1986 – Major League Baseball’s Rules Committee votes to change the designated hitter rule for the World Series, allowing a DH to be used in all games played in the American League club’s home park, but not in the National League’s. Since 1976, the DH had been used in all games in even years.

March 27, 1986
1986, March 27

On March 27, 1986 — 1986 – Major League Baseball’s Rules Committee votes to change the designated hitter rule for the World Series, allowing a DH to be used in all games played in the American League club’s home park, but not in the National League’s. Since 1976, the DH had been used in all games in even years.

Sources –
Baseball Reference March 27
SABR Games Project
National Pastime March 27
Retro Sheet
Replay The Game