As an EU Member State, Greece uses the euro (€). Just like other Member States, it uses 6 subdivisions of the euro, i.e. €0.01, €0.02, €0.05, €0.10, €0.20 and €0.50 (cents), and €1,00 and €2.00 coins. It also uses the following banknotes: €5.00, €10.00, €20.00, €50.00, €100.00, €200.00 and €500.00.
You can exchange your foreign currency in all banks that accept foreign currency and provide a detailed list of foreign exchange rates.
Greek banks are open five days a week, from Monday to Thursday from 08:00-14:30 and on Friday from 08:00-13:30.
Of course, credit card holders can use ATMs on a 24-hour basis.
You can also exchange your foreign currency in duly authorized offices in large cities. You will have to produce your passport.