In Barcelona, and throughout Catalonia, there are two official languages: Catalan, the language of the Catalans, and Spanish, the official language of Spain. As in most European countries and also in Catalonia, GMT is the time system used in Barcelona. Clocks are one hour ahead of GMT in winter and two in summer and are adjusted twice a year, going forward one hour in winter and back an hour in summer. Spain is in the Eurozone and the euro is its official currency. Foreign currency can be exchanged at banks (Monday to Friday, 8.30am to 2pm) and at the bureaux de change also open every day in Barcelona city centre, and at the main railway stations and the Estació del Nord bus station and at the Airport, where they have longer opening hours.