Question: National Sports Stadium is a multi-purpose stadium in Ulaanbaatar, Mongolia, The Naadam festival, which celebrates Mongolian independence, is held there every when? 

full_context: Document 1: Khorol (game): Khorol or Khorlo (Mongolian: Хорол or Хорло) is a multi-trick tile-based game played in Mongolia, Inner Mongolia, and Tuva, usually on Lunar New Year's. It is played between two and eight players with four being the most common. The game appeared during Manchu rule (1645-1912).
Document 2: National Stadium (Tokyo): National Stadium (国立競技場 , Shin kokuritsu kyōgijō ) was a multi-purpose stadium in Kasumigaoka, Shinjuku, Tokyo, Japan. The stadium served as the main stadium for the opening and closing ceremonies, as well as being the venue for track and field events at the 1964 Summer Olympic Games. The Japan national football team's home matches and major football club cup finals were held at the stadium. The stadium's official capacity was 57,363, but the real capacity was only 48,000 seats.
Document 3: 1989 Mongolian National Championship: The 1989 Mongolian National Championship was the twenty-fifth recorded edition of the Mongolian National Championship for football, with the first tournament taking place in 1955 and no tournament held in 1965 or apparently in 1977. It would appear however that championships were contested between 1956 and 1963, as sources note that a team called Aldar, the Mongolian Army Sports Club, won the title on numerous occasions during that time. Nonetheless, the 1989 national championship was won for the fourth time by Khuldumur (literally: "Labour" or "Workers" and also romanised as Hödölmör) and the first time since their success in the 1972 season
Document 4: National Sports Stadium (Mongolia): National Sports Stadium is a multi-purpose stadium in Ulaanbaatar, Mongolia. It is used mostly for football matches and has a capacity 12,500. The Naadam festival, which celebrates Mongolian independence, is held there every July. The land owned by the stadium company is about 27 hectares, of which the stadium takes about 8 hectares of land. The National Sport Stadium in Mongolia hosted the 2016 World University Archery Championship.
Document 5: Naadam: Naadam (Mongolian: Наадам , classical Mongolian: "Naɣadum", ] , "literally "games"") is a traditional festival in Mongolia. The festival is also locally termed "eriin gurvan naadam" (эрийн гурван наадам ) "the three games of men". The games are Mongolian wrestling, horse racing, and archery, and are held throughout the country during midsummer. Women have started participating in the archery and girls in the horse-racing games, but not in Mongolian wrestling.
Document 6: Mongol Derby: The Mongol Derby is an equestrian endurance race. The race extends 1000 km through the Mongolian Steppe and is known as the world's longest horse race. The course recreates the horse messenger system developed by Ghengis Khan in 1224. In the 2016 race, there will be 21 men and 23 women playing the role of the messengers, and representing 13 countries. The exact course changes every year, and is kept secret until shortly before the race begins. The terrain will invariably include mountain passes, green open valleys, wooded hills, river crossings, wetland and floodplains, sandy semi-arid dunes, rolling hills, dry riverbeds and of course open steppe. The entry fee is $13,000, and provides the rider access to 30 Mongolian horses, a support team, pre-race training, and access to the support stations along the way. Riders must change horses every 40 km at the support stations. Along the way are vet checks to monitor the condition of the horses, and the vets may impose time penalties if the riders push their horses too hard along the trail. To gain entry as a competitor, each rider must demonstrate that their riding skills are strong enough to endure the harsh terrain of the race. The horses themselves are semi-wild, and may not cooperate with the rider, adding one more level of difficulty to the race. Riders will spend thirteen to fourteen hours a day in the saddle, and the race lasts ten days. To complete the race is an accomplishment in and of itself, as only half the racers usually finish the race in any given year.
Document 7: 1987 Mongolian National Championship: The 1987 Mongolian National Championship was the twenty-third recorded edition of the Mongolian National Championship for football, with the first tournament taking place in 1955 and no tournament held in 1965 or apparently in 1977. It would appear however that championships were contested between 1956 and 1963, as sources note that a team called Aldar, the Mongolian Army Sports Club, won the title on numerous occasions during that time. Nonetheless, the 1985 national championship was won for the first time by Sükhbaatar, a team representing Sükhbaatar District, one of nine Düüregs (districts) of the capital Ulaanbaatar. Strength, a team representing the Public Security Sports Association, finished as runners up, whilst a team representing October District in Ulaanbaatar finished in third place.
Document 8: Rungrado 1st of May Stadium: The Rungrado 1st of May Stadium, also known as the May Day Stadium, is a multi-purpose stadium in Pyongyang, North Korea, completed on 1 May 1989. It is the largest stadium in the world, with a total capacity of 114,000. The site occupies an area of 20.7 ha .
Document 9: Addis Ababa National Stadium: Addis Ababa National Stadium will be a multi-purpose stadium, which can host football, rugby and athletics, in Bole, in eastern Addis Ababa, Ethiopia. It will be the national stadium of the Ethiopia national football team. The stadium will have a capacity of 60,000 and will be built by the Chinese State Construction Engineering Corporation. While the stadium itself will cover 37 hectares, development is planned around it, spanning across 60 hectares.
Document 10: Mongolia national football team results: The Mongolia national football team represents Mongolia in international football under the control of the Mongolian Football Federation. Founded in 1959, the federation was inactive between 1961 and 1997 and the men's national team did not feature in any international fixtures during that time. The federation was reorganized in 1997 and joined the AFC the same year. In 1998 the federation became a full member of FIFA, the international governing body for the sport. The MFA joined the EAFF as one of eight founding members in May 2002. Because of the harsh climate and a lack of suitable venues, the team has hosted few home matches in the past. However, in 2002 the MFF, with assistance from FIFA, began developing facilities in the country, including the creation of the 5,000-seat MFF Football Centre, which will allow the team to play more matches in Mongolia. About Mongolia's relatively low number of matches played, former national team player and coach Zorigtyn Battulga said, "Lack of games is a problem. No one will come to Mongolia in December and for us to fly to other countries is very expensive so it’s hard to arrange official matches."
Document 11: Philippine Sports Stadium: The Philippine Sports Stadium, also known as New Era University (NEU) Stadium, is a football and track stadium at Ciudad de Victoria, a 140-hectare tourism enterprise zone in the towns of Bocaue and Santa Maria in Bulacan, Philippines. The stadium was built right next to the Philippine Arena, the world's largest indoor arena. The stadium is the largest football stadium in the Philippines with a maximum seating capacity of 25,000. Its seating capacity is more than twice the seating capacity of the Rizal Memorial Stadium, the national stadium of the country which has a seating capacity of 12,000.
Document 12: Women's mixed martial arts: While mixed martial arts is primarily a male dominated sport, it does have female athletes. Female competition in Japan includes promotions such as DEEP Jewels. Now defunct promotions that featured female fighters were Valkyrie, and Smackgirl. Professional mixed martial arts organizations in the United States that invite women to compete are industry leader Ultimate Fighting Championship, the all female Invicta Fighting Championships, Resurrection Fighting Alliance, Bellator Fighting Championships, and Legacy Fighting Championship. Now defunct promotions that featured female fighters were Strikeforce and EliteXC.
Document 13: National Sports Stadium (Zimbabwe): The National Sports Stadium is a multi-purpose stadium, in Harare, Zimbabwe, with a capacity of 60,000 people. It is used mostly for football matches, but is also used for rugby union. CAPS United F.C. use the venue, which opened in 1987, for most of their home games.
Document 14: 1974 Mongolian National Championship: The 1974 Mongolian National Championship was the eleventh recorded edition of the Mongolian National Championship for football, with the first tournament taking place in 1955 and no tournament held in 1965. The 1974 national championship was won by Aldar (literally "Glory"; a team representing the Army sports society) their second recorded title, following their victory in the 1970 championship. Though it would appear however that championships were contested between 1956 and 1963, as sources note that a team called Aldar, the Mongolian Army Sports Club, won the title on numerous occasions during that time. Zamchin, a team representing railway workers finished as runners up, with Darkhan, representing the city of Darkhan, the capital of Darkhan-Uul Aimag, the 1968 champions, finishing third.
Document 15: Jenadriyah: Al-Jenadriyah (Arabic: مهرجان الجنادرية Maharajān al-Janādrīyah) is a cultural and heritage festival held in Jenadriyah (or Janadriyah) near Riyadh in Saudi Arabia each year, lasting for two weeks. It is organised by the National Guard, and the first was held in 1985. Activities include a camel race, performance of local music and dancing of the Ardah and the Mizmar. The festival draws more than one million visitors every year. The festival "normally falls during the month of February or March...Long ago, Janadriyah was known as 'Rowdhat Souwais' and was mentioned by numerous historians and writers."
ground_truth: July