The 50-contract limit has an interesting distinction in that the limit pertains to the season(s) for which a contract is valid. All NHL player contracts expire on June 30. The year varies from contract to contract, but the day remains the same (as we’ll discuss more when we look at player contracts in later editions of the feature). Knowing it has expiring contracts coming off its 50-contract maximum, a team can sign players to contracts for the following season. By doing so a team may have more than 50 different players signed to valid SPCs, as long as 50 or fewer are signed to valid SPCs for that current season AND fewer than 50 SPCs on tap for the upcoming season.
The 23-man roster limit is in place from the conclusion of the preseason until 12:01 am on the day of the NHL’s Trade Deadline. After that teams are allowed to have an unlimited active roster at the NHL level, provided players are signed to one of their 50 contract slots. NHL teams are only allowed to dress a maximum of 20 players – 18 skaters and two goaltenders – for any given game, but those 20 must come from the 23-player active roster.
Nashville Predators - Features: The Business of the Game: Roster Limits - 07/11/2008 
The Business of the Game: Roster Limits (NHL) 
