Question: When did Bayern Munich win their first competitive game under Barcelona's former manager?

Context paragraphs:
2011 Audi Cup: The second edition of the Audi Cup was a two-day association football tournament that featured four teams.  It was played at the Allianz Arena in Munich, Germany.  The competition hosted the defending champions Bayern Munich, the 2010 Copa Libertadores champions Internacional, the 2010–11 UEFA Champions League winners Barcelona and the 2007 FIFA Club World Cup champions Milan.  The winners of the tournament were Barcelona, beating Bayern Munich 2–0 in the final.  Internacional defeated Milan in the third place match after a penalty shoot-out.

2009–10 FC Bayern Munich season: The 2009–10 season of Bayern Munich began on 1 July with their first training session, led by the team's new head coach Louis van Gaal.  After several friendlies the first competitive game was a cup game on 1 August.  The league started on 8 August.

1987–88 FC Bayern Munich season: The 1987–88 FC Bayern Munich season was the 88th season in the club's history and 23rd season since promotion from Regionalliga Süd in 1965.  Bayern Munich finished as runner-up in the Bundesliga to SV Werder Bremen.  The club reached the quarterfinals of both the DFB-Pokal and the European Cup.  The inaugural DFB-Supercup was won by Bayern Munich over Hamburger SV.  This season was the first season under manager Jupp Heynckes, who replaced Udo Lattek.

Louis van Gaal: Aloysius Paulus Maria "Louis" van Gaal, (] ; born 8 August 1951) is a Dutch football manager and former player.  He was formerly manager of Ajax, Barcelona, AZ, Bayern Munich, the Netherlands and Manchester United.  He is one of the most decorated managers in world football, having won 20 major honours in his managerial career.

FC Bayern Munich Junior Team: The FC Bayern Munich Junior Team is the youth academy for German football club Bayern Munich.  The Junior Team was created in 1902 and restructured in 1995.  It has educated many players who have become regulars in the Bundesliga and Germany.  The vision for the Junior Team is ""to educate young players so that it will be possible for FCB to keep a global position in club football in the next millennium and its mission is "to have the best youth development in club football.  Bayern Munich have to test before the school will accept and you can study free until you graduate if you have a talent.""  Rosters remain unchanged while players train for their position.  Bayern Munich Junior Team uses a 4–3–3 formation good system.  Bayern Munich has scouts all over the world.  Bayern Munich has developed a ""Talent Day"".  In 2003, Bayern Munich started partnering with other football clubs.  The penultimate stage for youngsters at Bayern is Bayern Munich II.

1994–95 FC Bayern Munich season: The 1994–95 FC Bayern Munich season was the 95th season in the club's history and 30th season since promotion from Regionalliga Süd in 1965.  The first competitive match was the DFB-Supercup on 7 August which Bayern lost to SV Werder Bremen after 120 minutes of play.  The Bundesliga campaign ended with a sixth-place finish.  The club lost the first game of the DFB-Pokal.  This loss caused the third exit after one match since 1990–91.  Bayern made it to the semifinals of the Champions League before being eliminated by Ajax.  Giovanni Trapattoni managed the club for one season before returning in 1996–97.

1984–85 FC Bayern Munich season: The 1984–85 FC Bayern Munich season was the 85th season in the club's history.  Bayern Munich won its 7th Bundesliga title, reached the semi-final of UEFA Cup Winners' Cup, and finished as runner-up of DFB-Pokal.  This season was the second season of Udo Lattek's second stint as manager of the club.  The Bundesliga campaign started 25 August 1984 with a 3-1 victory over Arminia Bielefeld.  Bayern Munich, 1.  FC Köln, and Borussia Monchengladbach were tied for first place after Round 1.  From Round 2 through Round 34 of the season, Bayern Munich were the lone team in first place.  Qualification for the 1984–85 European Cup Winners' Cup was a result of winning the 1983–84 DFB-Pokal.

Uli Hoeneß Cup: The Uli Hoeneß Cup was a pre-season association football match that took place on 24 July 2013 at the Allianz Arena in Munich, Germany.  The competition featured hosts and 2012–13 UEFA Champions League winner Bayern Munich and the 2012–13 Spanish champions Barcelona.  The game was the first that Bayern Munich's new manager Pep Guardiola contested against his former club Barcelona and was a late 60th birthday present for Bayern Munich club president Uli Hoeneß.  The entire proceeds were donated towards social purposes.  The original planned kick-off time (20:30) was changed because of the 2013 UEFA Women's Championship semi-final match between Sweden and Germany.

2012–13 DFB-Pokal: The 2012–13 DFB-Pokal was the 70th season of the annual German football cup competition.  It began on 17 August 2012 with the first of six rounds and ended on 1 June 2013 with the final at the Olympic Stadium in Berlin.  The defending champions were Borussia Dortmund, but they were beaten by Bayern Munich in the quarter-finals.  Bayern Munich went on to win the competition, defeating VfB Stuttgart 3–2 in the final.  As runners-up, VfB Stuttgart have qualified for the third qualifying round of the 2013–14 UEFA Europa League, since Bayern Munich won the Bundesliga and will be competing in the 2013–14 UEFA Champions League.

1990–91 FC Bayern Munich season: The 1990–91 FC Bayern Munich season was the 91st season in the club's history and 26th season since promotion from Regionalliga Süd in 1965.  Bayern finished three points behind champions 1.  FC Kaiserslautern in the Bundesliga.  In the DFB-Pokal, Bayern were eliminated in the first round for the first time in club history.  Bayern reached the semifinals of the European Cup before being eliminated by Red Star Belgrade due to an own goal in the 90th minute of the second leg.  The first competitive match of the season was the DFB-Supercup on 31 July which Bayern won by a score of 4–1 over 1.  FC Kaiserslautern.

Supporting paragraphs: 2009–10 FC Bayern Munich season Louis van Gaal
Answer: 1 August