Question: When did Swedish become the official language of the country where the performer of Best Of is based?

full_context: Document 1: Best of 061122‒071122: Best of 061122‒071122 is the first compilation album released by Swedish Singer-songwriter Miss Li. Released on December 25, 2007, her fourth album in just over a year, the album debuted at #29 on the Swedish albums chart, but reached a peak at #11 in August 2008.
Document 2: Best of the Beast: Best of the Beast was Iron Maiden's first "best of" album, released in 1996 in three formats: a 34 track (four disc) vinyl, a 27 track (two disc) CD, a 16 track (single disc) CD and MiniDisc. The vinyl edition is, to date, the band's longest record release, running for over three hours.
Document 3: Best of Hilary Duff: Best of Hilary Duff is the first greatest hits album by American recording artist Hilary Duff. It was released on November 11, 2008, by Hollywood Records. The 12-track album consists of eight of Duff's previous singles, as well as two new recordings: "Reach Out" and "Holiday", and two remixes to the songs. Only one single was released from the album, the Ryan "Alias" Tedder-produced "Reach Out", which became her third single to chart at number one on the "Billboard" Hot Dance Club Play. Despite being a greatest hits album, her singles "Someone's Watching Over Me", "Our Lips Are Sealed" and "Beat of My Heart" aren't included in the standard edition of the album.
Document 4: Hep Stars: The Hep Stars were a Swedish rock group, formed in 1963 in Stockholm. During 1965-66 the band was the most successful of contemporary 1960s Swedish pop groups performing in the English language. Outside The Nordic Countries the band is best known as a launching point for the keyboard player and composer Benny Andersson, who went on to enjoy worldwide success with ABBA.
Document 5: Bengt Lagerberg: Bengt Lagerberg (born 5 July 1973), is best known as the drummer in the Swedish rock band The Cardigans. He is currently living in Malmö.
Document 6: Lovefool: ``Lovefool ''is a song written by Peter Svensson and Nina Persson for The Cardigans' third studio album, First Band on the Moon (1996). It was released as a single on 14 September 1996 in the United Kingdom and internationally on 5 October 1996. It was released as the album's lead single in 1996 and became the Cardigans' first international hit single, topping the Billboard Hot 100 Airplay chart and making appearances on six other Billboard charts. In 1997, the song found international success, peaking at number two on the UK Singles Chart and finding moderate success on some other European charts. The single also topped the charts in New Zealand, and was certified Gold in Australia.
Document 7: Dutch language: Old Dutch naturally evolved into Middle Dutch. The year 1150 is often cited as the time of the discontinuity, but it actually marks a time of profuse Dutch writing and during this period a rich Medieval Dutch literature developed. There was at that time no overarching standard language; Middle Dutch is rather a collective name for a number of closely related dialects whose ancestor was Old Dutch. But they were all mutually intelligible. In fact, since Dutch is a rather conservative language, the various literary works of that time today are often very readable for modern-day speakers.
Document 8: Friends (Swedish band): Friends was a Swedish "dansband" or pop group formed in 1999 and made up of Stefan Brunzell, Tony Haglund, Kristian Hermanson, Nina Inhammar, Kim Kärnfalk and Peter Strandberg. They were put together from auditions on the reality television show Friends på turne ("Friends on Tour"), made by Bert Karlsson for TV4. The show was a success and Friends competed on Melodifestivalen 2000, reaching second place. They won Melodifestivalen 2001 with "Lyssna till ditt hjärta" and represented Sweden at the Eurovision Song Contest 2001 with the English version of the song, "Listen to Your Heartbeat" wearing sexy, tight, leather fitted clothing. Prior to the Eurovision performance, the Swedish delegation was forced to pay royalties to the team behind "Liefde is een kaartspel", an earlier Belgian entry, making the song the first admitted case of plagiarism in Eurovision history.
Document 9: Best Of (The Cardigans album): Best Of is a greatest hits album by the Swedish group The Cardigans, released in Europe in January 2008. It contains twenty-one singles and album tracks. There is also a double-CD version with rare tracks and B-sides. Both versions of the album contain no new songs, though some tracks had previously been released only in the UK or Japan.
Document 10: Old English: Old English developed from a set of Anglo-Frisian or North Sea Germanic dialects originally spoken by Germanic tribes traditionally known as the Angles, Saxons, and Jutes. As the Anglo-Saxons became dominant in England, their language replaced the languages of Roman Britain: Common Brittonic, a Celtic language, and Latin, brought to Britain by Roman invasion. Old English had four main dialects, associated with particular Anglo-Saxon kingdoms: Mercian, Northumbrian, Kentish and West Saxon. It was West Saxon that formed the basis for the literary standard of the later Old English period, although the dominant forms of Middle and Modern English would develop mainly from Mercian. The speech of eastern and northern parts of England was subject to strong Old Norse influence due to Scandinavian rule and settlement beginning in the 9th century.
Document 11: Switzerland: Aside from the official forms of their respective languages, the four linguistic regions of Switzerland also have their local dialectal forms. The role played by dialects in each linguistic region varies dramatically: in the German-speaking regions, Swiss German dialects have become ever more prevalent since the second half of the 20th century, especially in the media, such as radio and television, and are used as an everyday language, while the Swiss variety of Standard German is almost always used instead of dialect for written communication (c.f. diglossic usage of a language). Conversely, in the French-speaking regions the local dialects have almost disappeared (only 6.3% of the population of Valais, 3.9% of Fribourg, and 3.1% of Jura still spoke dialects at the end of the 20th century), while in the Italian-speaking regions dialects are mostly limited to family settings and casual conversation.
Document 12: The Cardigans: The Cardigans are a Swedish rock band formed in Jönköping, Sweden, in 1992 by guitarist Peter Svensson, bassist Magnus Sveningsson, drummer Bengt Lagerberg, keyboardist Lars-Olof Johansson and lead singer Nina Persson. The group's line-up has been very stable, the only change being that their post-hiatus shows since 2012 have been with Oskar Humlebo on guitar instead of Svensson.
Document 13: Old English: Old English is a West Germanic language, developing out of Ingvaeonic (also known as North Sea Germanic) dialects from the 5th century. It came to be spoken over most of the territory of the Anglo-Saxon kingdoms which became the Kingdom of England. This included most of present-day England, as well as part of what is now southeastern Scotland, which for several centuries belonged to the Anglo-Saxon kingdom of Northumbria. Other parts of the island – Wales and most of Scotland – continued to use Celtic languages, except in the areas of Scandinavian settlements where Old Norse was spoken. Celtic speech also remained established in certain parts of England: Medieval Cornish was spoken all over Cornwall and in adjacent parts of Devon, while Cumbric survived perhaps to the 12th century in parts of Cumbria, and Welsh may have been spoken on the English side of the Anglo-Welsh border. Norse was also widely spoken in the parts of England which fell under Danish law.
Document 14: Languages of Sweden: Swedish evolved from Old Norse around the 14th and 15th century, and historically, the Swedish dialects were generally much more different than today. Since the 20th century Standard Swedish prevails throughout the country. The Scandinavian languages constitute a dialectal continuum and some of the traditional Swedish dialects could equally be described as Danish (Scanian) or Norwegian (Jamtlandic).
Document 15: The Cardigans discography: The Cardigans are a band from Sweden. They have released 6 studio albums which in total have sold about 15 million copies worldwide. This is a list of their album and single releases.
ground_truth: 20th century
sub_queries: Best Of >> performer Answer: The Cardigans
What country released The The Cardigans ? Answer: Sweden
when did swedish become the official language of Sweden Answer: 20th century