Q: Passage: Following the lead of minor leagues, as of the 2005 -- 06 season, the NHL ends exhibition and regular season games still tied after a five-minute-length, three-skaters-per-side overtime period (as of the 2015 -- 16 NHL season onwards) with a shootout. The NHL format is a three-round shootout with tiebreaker rounds as needed. All skaters (except goalies) on a team's roster must shoot before any player can shoot a second time. On December 16, 2014 the longest shootout in NHL history went to 20 rounds before Nick Bjugstad of the Florida Panthers scored to defeat the Washington Capitals; the previous record was 15 rounds.

Question: Based on this passage, what was the longest shootout in nhl history?
Let's give stream of consciousness below
To answer the above question, the relevant sentence is: On December 16, 2014 the longest shootout in NHL history went to 20 rounds before Nick Bjugstad of the Florida Panthers scored to defeat the Washington Capitals; the previous record was 15 rounds. So the answer is 20 rounds.