Question: The 2010–11 Tour de Ski was the 5th edition of the Tour de Ski and took place from 31 December 2010 to which date, Swiss cross-country skier, Dario Cologna won the Men's class?

full_context: Document 1: 2008–09 Tour de Ski: The 2008–09 Tour de Ski was the 3rd edition of the Tour de Ski and took place from 27 December 2008 until 4 January 2009. The race kicked off in Oberhof, Germany, and finished in Val di Fiemme, Italy. The men's event was 102 km, won by Dario Cologna of Switzerland; and the woman's event was 60 km, won by Virpi Kuitunen of Finland.
Document 2: 2012–13 Tour de Ski: The 2012-13 Tour de Ski was the 7th edition of the Tour de Ski. The event began in Oberhof, Germany on December 29, 2012, and ended in Val di Fiemme, Italy on January 6, 2013. The women's cup was won by defending champion Justyna Kowalczyk (Poland) while the men's cup was won by Russian Alexander Legkov ahead of defending champion Dario Cologna of Switzerland.
Document 3: Tour de Ski: The Tour de Ski (TdS) is a cross-country skiing event held annually since the 2006-2007 season in Central Europe, modeled on the Tour de France of cycling. Each Tour de Ski has consisted of six to nine stages, held during late December and early January in the Czech Republic, Germany, Italy, and Switzerland. The prize money for the event amount to 1,055,000 Swiss francs (844,000 euros), shared out on both men and women. Men's and women's events are held together on the same days, with the only difference being the distance skied.
Document 4: Dario Cologna: Dario Cologna (born 11 March 1986) is a Swiss cross-country skier. He has four overall World Cup victories, three Olympic gold medals, one World Championships gold medal and three Tour de Ski victories in his career so far.
Document 5: 2013–14 Tour de Ski: The 2013-14 Tour de Ski was the 8th edition of the Tour de Ski. The Stage World Cup event began in Oberhof, Germany on December 28, 2013, and ended in Val di Fiemme, Italy on January 5, 2014. The cups are being defended by Justyna Kowalczyk (Poland) and Alexander Legkov (Russia). The "last minute changes" introduced by the organizers of 2013-14 edition of Tour de Ski resulted in controversies regarding the balance between the free and classical techniques in the competition. Some people, including the four times winner of Tour de Ski and Olympic Champion Justyna Kowalczyk, resigned from participation in protest against changes excessively favoring freestyle competitors.
Document 6: 2010–11 Tour de Ski: The 2010–11 Tour de Ski was the 5th edition of the Tour de Ski and took place from 31 December 2010 to 9 January 2011. The race started in Oberhof, Germany, and ended in Val di Fiemme, Italy. The defending champions were Lukáš Bauer of the Czech Republic for the men and Poland's Justyna Kowalczyk for the women. Kowalczyk defende her title, and Swiss Dario Cologna won the Men's class.
Document 7: Janica Kostelić: Janica Kostelić (] ; born 5 January 1982) is a former World Cup alpine ski racer and four-time Olympic gold medalist from Croatia. In addition to the Olympics, she has won five gold medals at the World Championships. In World Cup competition, she has won thirty individual races, three overall titles, three slalom titles, and four (unofficial) combined titles. Kostelic's accomplishments in professional skiing have led some commentators, writers, and fellow ski racers to regard her as the greatest female ski racer of all time.[a]
Document 8: 2011–12 Tour de Ski: The 2011–12 Tour de Ski was the 6th edition of the Tour de Ski and took place from 29 December 2011 to 7 January 2012. The race started in Oberhof, Germany, and ended in Val di Fiemme, Italy. The defending champions were Dario Cologna of Switzerland for the men and Poland's Justyna Kowalczyk (2-time defending champion) for the women. Both Cologna and Kowalczyk were able to defend their titles as Tour de Ski champions and became the first athletes ever to win the Tour three times.
Document 9: Gianluca Cologna: Gianluca Cologna (born 17 May 1990) is a Swiss cross-country skier. His brother Dario Cologna is also a professional cross-country skier. He competed in the 2014 Winter Olympics in the Men's team sprint with his brother Dario and finished 5th in the final.
Document 10: Simon Ammann: Simon Ammann ( ; born 25 June 1981) is a Swiss ski jumper. He is one of the most successful athletes in the history of the sport, having won four individual Winter Olympic gold medals, in 2002 and 2010, and is the only ski jumper to have achieved the gold double–double at the Winter Olympics. Additionally he won the 2007 Ski Jumping World Championships; the 2010 Ski Flying World Championships; the 2010 Nordic Tournament; and the 2010 Ski Jumping World Cup.
Document 11: Gregor Schlierenzauer: Gregor Schlierenzauer (] ; born 7 January 1990) is an Austrian ski jumper. He is one of the sport's most successful athletes of all time, having won the Ski Jumping World Cup, Four Hills Tournament, and Nordic Tournament twice each; the Ski Flying World Cup three times; as well as four medals at the Winter Olympics, five at the Ski Flying World Championships, and twelve at the Ski Jumping World Championships.
Document 12: 2009–10 Tour de Ski: The 2009–10 Tour de Ski was the 4th edition of the Tour de Ski and took place 1–10 January 2010. The race started in Oberhof, Germany, and ended in Val di Fiemme, Italy. The defending champions are Switzerland's Dario Cologna for the men and Finland's Virpi Kuitunen. This year's event was won by Lukáš Bauer of the Czech Republic for the men and Poland's Justyna Kowalczyk for the women.
Document 13: Switzerland at the 2014 Winter Olympics: Switzerland competed at the 2014 Winter Olympics in Sochi, Russia, from 7 to 23 February 2014. 163 athletes were participating, making it the largest team Switzerland has ever sent to the Olympic Winter Games. The four-time Olympic gold medalist Simon Ammann was the flag bearer for the opening ceremony.
Document 14: 2014 Winter Olympics medal table: The 2014 Winter Olympics, officially known as the XXII Olympic Winter Games, were a winter multi-sport event held in Sochi, Russia, from 7 February to 23 February. A total of 2,873 athletes from 88 nations participated in 98 events in 7 sports across 15 different disciplines. Of all athletes, 187 of them representing 26 different countries won medals. The Netherlands achieved four podium sweeps in the speed skating, dominating the men's 500 metres, men's 5,000 metres, men's 10,000 metres, and women's 1,500 metres, surpassing the previous record of two podium sweeps. Host nation Russia matched the Soviet Union's 1976 achievement of thirteen gold medals and achieved the leading position on the medal table, making the 2014 Winter Games the fourth where the host nation topped the gold medal count. Slovenia won its first gold medal in alpine skiing, in the first Winter Olympic gold medal tie. Luger Armin Zöggeler of Italy became the first athlete to achieve six Winter Olympic medals over six consecutive games, all achieved at the men's singles event.
Document 15: Marit Bjørgen: Marit Bjørgen (born 21 March 1980) is a Norwegian cross-country skier and six times Olympic champion from Midtre Gauldal, Norway. She is ranked first in the all-time Cross-Country World Cup rankings with 106 individual victories. Bjørgen is also the most successful sprinter in Cross-Country World Cup history, with twenty-nine victories. One of her most notable achievements was becoming the most successful athlete at the 2010 Winter Olympics by winning five medals, including three gold medals. She also won three gold medals at the 2014 Winter Olympics. With her 2014 medals, she became, alongside Raisa Smetanina and Stefania Belmondo, the most medaled female Winter Olympian. However, she has more gold medals amongst her 10 Olympic medals than either of them. She is well known for her endurance, fitness, technical strength, mental toughness, and also her finishing sprints. She excels equally in both classic and skate style skiing, and does well through all distances from the sprint events to the long distance ones.
ground_truth: 9 January 2011