The biggest rule change heading into this season stems from what is and isn't offsides. In 1929, the NHL introduced offsides into the game, preventing players to enter the offensive zone before the puck fully crosses the blue line. That rule has stood tall 91 years. This year, after many instances of controversial and inclusive plays at the blue line, the NHL has adjusted that rule.
The offsides rule has been tweaked. According to NHL rulebook, rule 83.1 a player's skate does not have to be on the ice outside of the offensive zone when the puck crosses the blue line to be onside, it only has to but over it, hovering onside. The rule states that "a player is on-side when either of his skates are in contact with the blue line, or on his own side of the line, at the instant the puck completely crosses the leading edge of the blue line."
"On his own side of the line shall be defined by a "plane" of the blue line which shall extend from the leading edge of the blue line upwards. If a player's skate has yet to break the "plane" prior to the puck completely crossing the leading edge, he is deemed to be on-side for the purpose of the off-side rule." Simply put, if a player's skate is in the air, but isn't completely in the offensive zone, he'll be considered onside.
This adjustment to the offsides rule comes in attempt to make the ruling more clear and to continue providing more offense within the game. Had this rule been intact last year, 14 more goals would have been permitted to stand.
