Slovakia
The Slovak Republic and the Czech Republic went their separate ways after 1 January 1993, an event sometimes called the Velvet Divorce. Slovakia has remained a close partner with the Czech Republic. Both countries co-operate with Hungary and Poland in the Visegrád Group. Slovakia became a member of NATO on 29 March 2004 and of the European Union on 1 May 2004. On 1 January 2009, Slovakia adopted the Euro as its national currency.
European Exchange Rate Mechanism
As of 2016, only the Danish krone participates in ERM II. The currencies of Sweden (the Swedish krona), the three largest countries which joined the European Union on 1 May 2004 (the Polish złoty, the Czech koruna, and the Hungarian forint), the two countries which joined on 1 January 2007 (the Bulgarian lev, and the Romanian leu) as well Croatia, which joined the EU on 1 July 2013 (the Croatian kuna), are required to join in accordance with the terms of the applicable treaties of accession.