Question: When did the La Liga season won by Deportivo La Coruña begin? 

Context paragraphs:
2011–12 Real Valladolid season: The 2011–12 Spanish football season is Real Valladolid's second season in the second level in Spanish football after being defeated 3–2 on aggregate against Elche in La Liga promotion play-off in June 2011.  This season will be the 31st of Real Valladolid in the second level in Spanish football.  The general coordinator during last season, Chuti Molina, left his work on 14 June, becoming Real Murcia general director.  On 17 June, Real Valladolid made official Abel Resino's detachment as he did not renew his contract as team manager.  On 4 July, Carlos Suárez announced he had bought 59% of the club shareholding, becoming shareholder of Real Valladolid, and therefore the owner of the entity.  At the same time he confirmed that he will not step down as chairman and, from the next day, news about the sporting aspect will be known.  Earlier on 6 July, the club became official the incorporation of the Serbian manager Miroslav Đukić for the next 3 seasons.  During that day, it also was confirmed that José Antonio García Calvo, general director, left his work. <br>Real Valladolid qualified in 3rd position in Segunda División, behind both Deportivo and Celta de Vigo, with 82 points.  It was the first time in the history that any team with 80+ points wasn't directly promoted to La Liga.  Deportivo de La Coruña beat Real Valladolid's points record, getting 91 points in the whole season.  The record was established by José Luis Mendilibar's team in 2007 when Real Valladolid scored 88 points and were champions. <br>The team had to play the Promotion play-off again, and got the promotion to 2012–13 La Liga by winning 3–0 on aggregate to Córdoba in the Semifinal and by 2–1 to AD Alcorcón in the Final.

1999–2000 FC Barcelona season: FC Barcelona did not repeat its successful season in 1998–99, and fell back to second in La Liga, as well as knocked out of the Champions League in the semi-finals.  Barcelona did not perform well in the mid season and lost the league title to Deportivo La Coruña just 5 points behind and Louis van Gaal was let go by the club, with former Real Betis coach Lorenzo Serra Ferrer taking over after 1999-2000 season.  Despite trophyless season, the side managed to reach the semi-finals of the UEFA Champions League, where it lost to eventual runners up Valencia.

1999–2000 La Liga: The 1999–2000 La Liga season, the 69th since its establishment, began on 21 August 1999 and ended on 20 May 2000.

Alexandre Guimarães: Alexandre Henrique Borges Guimarães (born November 7, 1959) is a Costa Rican retired footballer, who played in 1990 FIFA World Cup.  He was the Costa Rica national football team head coach in Korea-Japan 2002 and Germany 2006, and had successful runs with teams like Al Wasl in United Arab Emirates, Tianjin Teda in China and Deportivo Saprissa in Costa Rica.  His son Celso Borges currently plays for Deportivo La Coruña in Spanish La Liga.  He represented Costa Rica nationally, despite being born and raised in Brazil.  Currently, he manages ISL team, Mumbai City FC.

Deportivo La Coruña Brasil Futebol Clube: Deportivo La Coruña Brasil Futebol Clube, commonly known as La Coruña, is a Brazilian football club based in Rio de Janeiro, Rio de Janeiro state.

2000 Supercopa de España: The 2000 Supercopa de España was a Spanish football competition, played over two legs on 20 August and 27 August 2000.  It was contested by Espanyol, who were Spanish Cup winners in 1999–2000, and Deportivo La Coruña, who won the 1999–2000 Spanish League.

2016–17 Deportivo de La Coruña season: This article covers the 2016–17 season for Deportivo La Coruña.  They'll participate in the 2016–17 La Liga and the 2016–17 Copa del Rey.

2016 Montevideo Tournament: The 2016 Montevideo Tournament was a summer football friendly tournament organized by La Liga.  Matches were played at the Estadio Centenario in Montevideo.  Uruguayan clubs Nacional and Peñarol (Primera División) were joined by Spanish clubs Celta Vigo and Deportivo La Coruña (La Liga).  It was the inaugural edition of the competition.

Deportivo de La Coruña: Real Club Deportivo de La Coruña (] ; English: "Royal Sporting Club of La Coruña") is a professional football club based in the city of A Coruña (known in Spanish as La Coruña), Galicia, Spain.

1999–2000 Celta de Vigo season: RC Celta de Vigo contested La Liga, the UEFA Cup and Copa del Rey in the 1999-2000 season.  Being title contenders up until Christmas, Celta lost their form in the second half of the season, aside from a 4-0 victory against Juventus in the last 16 of the UEFA Cup.  The end result was 7th and quarter finals of the UEFA Cup, which meant the side missed out on Champions League football once again.  The club also missed the chance to become the first Spanish championship-winning team from Galicia, with arch rivals Deportivo La Coruña winning La Liga.

Supporting paragraphs: 2000 Supercopa de España 1999–2000 La Liga
Answer: 21 August 1999