What is the standard length of an NHL game?

A standard NHL game consists of three periods, each lasting 20 minutes, which totals to 60 minutes of gameplay. This duration is set in the NHL's rules and reflects the format that has been established for the league.

In addition to the regulation time, if the game is tied at the end of the three periods, there are overtime periods played, which can extend the length of the game. However, the standard gameplay time without accounting for any overtime or penalties is indeed 60 minutes.

The other answer choices reflect lengths that do not pertain to standard NHL games. Any length beyond 60 minutes typically involves either overtime or rare circumstances like shootouts, not standard playtime during a game. Thus, the widely accepted and definitive length of a regular NHL game is 60 minutes.