Question: When did Denmark join the market where 6th gen iPods limited the highest volume of the player?

full_context: Document 1: European Union law: The Social Charter was subsequently adopted in 1989 by 11 of the then 12 member states. The UK refused to sign the Social Charter and was exempt from the legislation covering Social Charter issues unless it agreed to be bound by the legislation. The UK subsequently was the only member state to veto the Social Charter being included as the "Social Chapter" of the 1992 Maastricht Treaty - instead, an Agreement on Social Policy was added as a protocol. Again, the UK was exempt from legislation arising from the protocol, unless it agreed to be bound by it. The protocol was to become known as "Social Chapter", despite not actually being a chapter of the Maastricht Treaty. To achieve aims of the Agreement on Social Policy the European Union was to "support and complement" the policies of member states. The aims of the Agreement on Social Policy are:
Document 2: IPod: In mid-2015, several new color schemes for all of the current iPod models were spotted in the latest version of iTunes, 12.2. Belgian website Belgium iPhone originally found the images when plugging in an iPod for the first time, and subsequent leaked photos were found by Pierre Dandumont.
Document 3: IPod: The third generation began including a 30-pin dock connector, allowing for FireWire or USB connectivity. This provided better compatibility with non-Apple machines, as most of them did not have FireWire ports at the time. Eventually Apple began shipping iPods with USB cables instead of FireWire, although the latter was available separately. As of the first-generation iPod Nano and the fifth-generation iPod Classic, Apple discontinued using FireWire for data transfer (while still allowing for use of FireWire to charge the device) in an attempt to reduce cost and form factor. As of the second-generation iPod Touch and the fourth-generation iPod Nano, FireWire charging ability has been removed. The second-, third-, and fourth-generation iPod Shuffle uses a single 3.5 mm minijack phone connector which acts as both a headphone jack and a data port for the dock.
Document 4: IPod: Before the release of iOS 5, the iPod branding was used for the media player included with the iPhone and iPad, a combination of the Music and Videos apps on the iPod Touch. As of iOS 5, separate apps named "Music" and "Videos" are standardized across all iOS-powered products. While the iPhone and iPad have essentially the same media player capabilities as the iPod line, they are generally treated as separate products. During the middle of 2010, iPhone sales overtook those of the iPod.
Document 5: IPod: In mid-2015, a new model of the iPod Touch was announced by Apple, and was officially released on the Apple store on July 15, 2015. The sixth generation iPod Touch includes a wide variety of spec improvements such as the upgraded A8 processor and higher-quality screen. The core is over 5 times faster than previous models and is built to be roughly on par with the iPhone 5S. It is available in 5 different colors: Space grey, pink, gold, silver and Product (red).
Document 6: IPod: iPod batteries are not designed to be removed or replaced by the user, although some users have been able to open the case themselves, usually following instructions from third-party vendors of iPod replacement batteries. Compounding the problem, Apple initially would not replace worn-out batteries. The official policy was that the customer should buy a refurbished replacement iPod, at a cost almost equivalent to a brand new one. All lithium-ion batteries lose capacity during their lifetime even when not in use (guidelines are available for prolonging life-span) and this situation led to a market for third-party battery replacement kits.
Document 7: IPod: From the fifth-generation iPod on, Apple introduced a user-configurable volume limit in response to concerns about hearing loss. Users report that in the sixth-generation iPod, the maximum volume output level is limited to 100 dB in EU markets. Apple previously had to remove iPods from shelves in France for exceeding this legal limit. However, users that have bought a new sixth-generation iPod in late 2013 have reported a new option that allowed them to disable the EU volume limit. It has been said that these new iPods came with an updated software that allowed this change. Older sixth-generation iPods, however, are unable to update to this software version.
Document 8: European Union law: EU Competition law has its origins in the European Coal and Steel Community (ECSC) agreement between France, Italy, Belgium, the Netherlands, Luxembourg and Germany in 1951 following the second World War. The agreement aimed to prevent Germany from re-establishing dominance in the production of coal and steel as members felt that its dominance had contributed to the outbreak of the war. Article 65 of the agreement banned cartels and article 66 made provisions for concentrations, or mergers, and the abuse of a dominant position by companies. This was the first time that competition law principles were included in a plurilateral regional agreement and established the trans-European model of competition law. In 1957 competition rules were included in the Treaty of Rome, also known as the EC Treaty, which established the European Economic Community (EEC). The Treaty of Rome established the enactment of competition law as one of the main aims of the EEC through the "institution of a system ensuring that competition in the common market is not distorted". The two central provisions on EU competition law on companies were established in article 85, which prohibited anti-competitive agreements, subject to some exemptions, and article 86 prohibiting the abuse of dominant position. The treaty also established principles on competition law for member states, with article 90 covering public undertakings, and article 92 making provisions on state aid. Regulations on mergers were not included as member states could not establish consensus on the issue at the time.
Document 9: European Union law: The primary law of the EU consists mainly of the founding treaties, the "core" treaties being the Treaty on European Union (TEU) and the Treaty on the Functioning of the European Union (TFEU). The Treaties contain formal and substantive provisions, which frame policies of the European Union institutions and determine the division of competences between the European Union and its member states. The TEU establishes that European Union law applies to the metropolitan territories of the member states, as well as certain islands and overseas territories, including Madeira, the Canary Islands and the French overseas departments. European Union law also applies in territories where a member state is responsible for external relations, for example Gibraltar and the Åland islands. The TEU allows the European Council to make specific provisions for regions, as for example done for customs matters in Gibraltar and Saint-Pierre-et-Miquelon. The TEU specifically excludes certain regions, for example the Faroe Islands, from the jurisdiction of European Union law. Treaties apply as soon as they enter into force, unless stated otherwise, and are generally concluded for an unlimited period. The TEU provides that commitments entered into by the member states between themselves before the treaty was signed no longer apply.[vague] All EU member states are regarded as subject to the general obligation of the principle of cooperation, as stated in the TEU, whereby member states are obliged not to take measure which could jeopardise the attainment of the TEU objectives. The Court of Justice of the European Union can interpret the Treaties, but it cannot rule on their validity, which is subject to international law. Individuals may rely on primary law in the Court of Justice of the European Union if the Treaty provisions have a direct effect and they are sufficiently clear, precise and unconditional.
Document 10: Accession of Turkey to the European Union: Turkey's application to accede to the European Economic Community, the predecessor of the European Union (EU), was made on 14 April 1987. After the ten founding members, Turkey was one of the first countries to become a member of the Council of Europe in 1949. The country has also been an associate member of the Western European Union from 1992 to its end in 2011. Turkey signed a Customs Union agreement with the EU in 1995 and was officially recognised as a candidate for full membership on 12 December 1999, at the Helsinki summit of the European Council.
Document 11: History of the European Union: On 1 November 1993, under the third Delors Commission, the Maastricht Treaty became effective, creating the European Union with its pillar system, including foreign and home affairs alongside the European Community. The 1994 European elections were held resulting in the Socialist group maintaining their position as the largest party in Parliament. The Council proposed Jacques Santer as Commission President but he was seen as a second choice candidate, undermining his position. Parliament narrowly approved Santer but his commission gained greater support, being approved by 416 votes to 103. Santer had to use his new powers under Maastricht to flex greater control over his choice of Commissioners. They took office on 23 January 1995.
Document 12: European Union law: The principal Treaties that form the European Union began with common rules for coal and steel, and then atomic energy, but more complete and formal institutions were established through the Treaty of Rome 1957 and the Maastricht Treaty 1992 (now: TFEU). Minor amendments were made during the 1960s and 1970s. Major amending treaties were signed to complete the development of a single, internal market in the Single European Act 1986, to further the development of a more social Europe in the Treaty of Amsterdam 1997, and to make minor amendments to the relative power of member states in the EU institutions in the Treaty of Nice 2001 and the Treaty of Lisbon 2007. Since its establishment, more member states have joined through a series of accession treaties, from the UK, Ireland, Denmark and Norway in 1972 (though Norway did not end up joining), Greece in 1979, Spain and Portugal 1985, Austria, Finland, Norway and Sweden in 1994 (though again Norway failed to join, because of lack of support in the referendum), the Czech Republic, Cyprus, Estonia, Hungary, Latvia, Lithuania, Malta, Poland, Slovakia and Slovenia in 2004, Romania and Bulgaria in 2007 and Croatia in 2013. Greenland signed a Treaty in 1985 giving it a special status.
Document 13: IPod: The iPod line can play several audio file formats including MP3, AAC/M4A, Protected AAC, AIFF, WAV, Audible audiobook, and Apple Lossless. The iPod photo introduced the ability to display JPEG, BMP, GIF, TIFF, and PNG image file formats. Fifth and sixth generation iPod Classics, as well as third generation iPod Nanos, can additionally play MPEG-4 (H.264/MPEG-4 AVC) and QuickTime video formats, with restrictions on video dimensions, encoding techniques and data-rates. Originally, iPod software only worked with Mac OS; iPod software for Microsoft Windows was launched with the second generation model. Unlike most other media players, Apple does not support Microsoft's WMA audio format—but a converter for WMA files without Digital Rights Management (DRM) is provided with the Windows version of iTunes. MIDI files also cannot be played, but can be converted to audio files using the "Advanced" menu in iTunes. Alternative open-source audio formats, such as Ogg Vorbis and FLAC, are not supported without installing custom firmware onto an iPod (e.g., Rockbox).
Document 14: European Union law: The Social Chapter is a chapter of the 1997 Treaty of Amsterdam covering social policy issues in European Union law. The basis for the Social Chapter was developed in 1989 by the "social partners" representatives, namely UNICE, the employers' confederation, the European Trade Union Confederation (ETUC) and CEEP, the European Centre of Public Enterprises. A toned down version was adopted as the Social Charter at the 1989 Strasbourg European Council. The Social Charter declares 30 general principles, including on fair remuneration of employment, health and safety at work, rights of disabled and elderly, the rights of workers, on vocational training and improvements of living conditions. The Social Charter became the basis for European Community legislation on these issues in 40 pieces of legislation.
Document 15: Treaties of the European Union: Two core functional treaties, the Treaty on European Union (originally signed in Maastricht in 1992) and the Treaty on the Functioning of the European Union (originally signed in Rome in 1957 as the Treaty establishing the European Economic Community), lay out how the EU operates, and there are a number of satellite treaties which are interconnected with them. The treaties have been repeatedly amended by other treaties over the 65 years since they were first signed. The consolidated version of the two core treaties is regularly published by the European Commission.
ground_truth: 1972
sub_queries: In what markets did 6th gen iPods limit the highest volume of the player? Answer: EU
When did Denmark join the EU ? Answer: 1972