The NHL primarily uses three brands for outdoor games: the Heritage Classic, Winter Classic, and Stadium Series. The Heritage Classic has been infrequently held five times, and has thus far featured match-ups between Canadian teams. The 2003 Heritage Classic between the Edmonton Oilers and Montreal Canadiens was the first outdoor regular season game in NHL history. This led to the annual Winter Classic, held on New Year's Day in the United States, starting with the 2008 game between the Pittsburgh Penguins and the Buffalo Sabres. The NHL then started the Stadium Series in 2014 for additional outdoor games. The number of Stadium Series games has varied per season (four in 2014, only one in 2015, two in 2016, and one per season since 2017). Both the Winter Classic and the Stadium series featured match-ups solely between American teams until the Toronto Maple Leafs' appearances in both the 2014 Winter Classic and the 2018 Stadium Series.