Banks usually are open 8:30 AM-2:30 PM during the week and 8:30 AM-1 PM on Saturday. However, May to September they're open only on weekdays. Savings-and-loans banks have a different schedule—for instance, Caja Madrid is open weekdays 8:15 AM-2 PM and Saturday 11 AM-1:30 PM, although the latter may vary slightly depending on the office size and location. Caja Madrid also has special offices that are open continuously every day until 7 PM or 7:45 PM in some of the city's key locations: train stations, airport terminals, and the city center (they've got one on Gran Vía 44). You'll find no trouble exchanging foreign currency into euros, especially in tourist areas (Puerta del Sol, Callao, Gran Ví), providing you intend to exchange reasonable amounts.