Question: When did the accident occur that the 2017 Joan Gamper Trophy held a tribute for?
Context: The Joan Gamper Trophy (Catalan: "Trofeu Joan Gamper" ) or Joan Gamper Cup is an annual friendly football match held in August, before the start of FC Barcelona's La Liga season.  The competition is hosted by FC Barcelona at the Camp Nou stadium and is named in honour of Joan Gamper, a founding member, player, and later president of the club.  The competition was inaugurated in 1966 by Enric Llaudet, one of Gamper's successors as club president.  The trophy itself is an 800 g silver cup with five micrometres of gold finishing, on top of a 10 kg marble plinth base. The 2015 Joan Gamper Trophy was the 50th edition of the Joan Gamper Trophy.  Spanish side and hosts Barcelona faced Italian side Roma at the Camp Nou in Barcelona.  This was Roma's first appearance in the Joan Gamper Trophy. The 2016 Joan Gamper Trophy was the 51st edition of the Joan Gamper Trophy.  Spanish side and hosts Barcelona faced Italian side Sampdoria at the Camp Nou in Barcelona.  This marked Sampdoria's third appearance in the Joan Gamper Trophy, after losing on penalties in 1997 and winning 1–0 in 2012. The 2012 Joan Gamper Trophy was the 47th edition of the Joan Gamper Trophy.  Spanish side and hosts Barcelona faced Italian side Sampdoria at the Camp Nou in Barcelona.  The Genovese club, in their second appearance after 1997, won their first ever Joan Gamper Trophy defeating the Catalans 1-0. LaMia Flight 2933 (LMI2933) was a charter flight of an Avro RJ85, operated by LaMia, which crashed in Colombia at 21:58 on 28 November 2016 killing 71 of 77 people on board.  The aircraft was transporting the Brazilian Chapecoense football squad's 22 players, 23 coaching and other staff, 2 guests and 21 journalists from Viru Viru International Airport in Santa Cruz de la Sierra , Bolivia, to José María Córdova International Airport in Colombia.  The team was scheduled to play the first leg of the 2016 Copa Sudamericana Finals in Medellín against Colombian team Atlético Nacional .  One of the four crew members, three of the players, and two other passengers survived. The Ciutat Esportiva Joan Gamper (] ) is the training ground and academy base of Catalan football club FC Barcelona.  It was officially opened on 1 June 2006, and was named in honor of Joan Gamper, founder of the club. The 2014 Joan Gamper Trophy was the 49th edition of the Joan Gamper Trophy.  Spanish side and hosts Barcelona faced Mexican side León at the Camp Nou in Barcelona.  This marked the first appearance of a North American team in the Joan Gamper Trophy. The 2017 Joan Gamper Trophy was the 52nd edition of the Joan Gamper Trophy.  Spanish side and hosts Barcelona faced Brazilian side Chapecoense at the Camp Nou in Barcelona.  This marked Chapecoense's first ever appearance in the Joan Gamper Trophy, as a tribute to the 71 Chapecoense players and staff who lost their lives after the LaMia Flight 2933 tragedy in La Unión, Colombia, on 28 November 2016. The 2013 Joan Gamper Trophy was the 48th edition of the Joan Gamper Trophy.  Spanish side and hosts Barcelona faced Brazilian side Santos at the Camp Nou in Barcelona.  This marked Barcelona's biggest win in the Joan Gamper Trophy with an eight-goal advantage. The 2011 Joan Gamper Trophy was the 46th edition of the Joan Gamper Trophy.  Spanish side and hosts Barcelona faced Italian side Napoli at the Camp Nou in Barcelona.
Answer: 28 November 2016