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Introduction

The euro was established by the provisions in the 1992 Maastricht Treaty. To participate in the currency, member states are meant to meet strict criteria, such as a budget deficit of less than 3% of their GDP, a debt ratio of less than 60% of GDP (both of which were ultimately widely flouted after introduction), low inflation, and interest rates close to the EU average. In the Maastricht Treaty, the United Kingdom and Denmark were granted exemptions per their request from moving to the stage of monetary union which resulted in the introduction of the euro (see also United Kingdom and the euro).

The name "euro" was officially adopted in Madrid on 16 December 1995. Belgian Esperantist Germain Pirlot, a former teacher of French and history, is credited with naming the new currency by sending a letter to then President of the European Commission, Jacques Santer, suggesting the name "euro" on 4 August 1995.

Due to differences in national conventions for rounding and significant digits, all conversion between the national currencies had to be carried out using the process of triangulation via the euro. The definitive values of one euro in terms of the exchange rates at which the currency entered the euro are shown in the table.

The rates were determined by the Council of the European Union, based on a recommendation from the European Commission based on the market rates on 31 December 1998. They were set so that one European Currency Unit (ECU) would equal one euro. The European Currency Unit was an accounting unit used by the EU, based on the currencies of the member states; it was not a currency in its own right. They could not be set earlier, because the ECU depended on the closing exchange rate of the non-euro currencies (principally pound sterling) that day.

The procedure used to fix the conversion rate between the Greek drachma and the euro was different since the euro by then was already two years old. While the conversion rates for the initial eleven currencies were determined only hours before the euro was introduced, the conversion rate for the Greek drachma was fixed several months beforehand.

The currency was introduced in non-physical form (traveller's cheques, electronic transfers, banking, etc.) at midnight on 1 January 1999, when the national currencies of participating countries (the eurozone) ceased to exist independently. Their exchange rates were locked at fixed rates against each other. The euro thus became the successor to the European Currency Unit (ECU). The notes and coins for the old currencies, however, continued to be used as legal tender until new euro notes and coins were introduced on 1 January 2002.

The changeover period during which the former currencies' notes and coins were exchanged for those of the euro lasted about two months, until 28 February 2002. The official date on which the national currencies ceased to be legal tender varied from member state to member state. The earliest date was in Germany, where the mark officially ceased to be legal tender on 31 December 2001, though the exchange period lasted for two months more. Even after the old currencies ceased to be legal tender, they continued to be accepted by national central banks for periods ranging from several years to indefinitely (the latter for Austria, Germany, Ireland, Estonia and Latvia in banknotes and coins, and for Belgium, Luxembourg, Slovenia and Slovakia in banknotes only). The earliest coins to become non-convertible were the Portuguese escudos, which ceased to have monetary value after 31 December 2002, although banknotes remained exchangeable until 2022.