Citizen Men's BT0004-57E Eco-Drive Calibre 3100 Twin Date Two-Tone Watch Light powered Eco-Drive Caliber E310 Japanese-quartz movement; charges in natural sunlight or indoor light Max power reserve: 1 year; low charge warning: 3 days; charge time from stop state to max charge: Incandescent Light - 230 hrs, Outdoors, Cloudy (10,000 Lux) - 70 hrs, Outdoors, Sunny (100,000 Lux) - 35 hrs Durable, hardened mineral crystal; case diameter: 43 mm Two-tone stainless steel case; black dial; perpetual-calendar functions Water resistant to 330 feet (100 M): suitable for snorkeling, as well as swimming, but not diving