January 1st, 2023
On January 1, 1999 the Euro became the new 'single currency' of the European Monetary Union. It was adopted by 11 Member States. Greece became the 12th Member state to adopt the Euro on January 1, 2001. On January 1, 2002, these 12 countries officially introduced the Euro banknotes and coins as legal tender.
Source: www.oanda.com/currency/help/euro