Ecologically friendly, light powered Eco-Drive Caliber E87* Japanese-quartz movement; Charges in natural sunlight or indoor light Max power reserve: 180 days; Low charge warning: 3 days; Charge time from stop state to max charge: Incandescent Light - 150 hours, Outdoors, Cloudy (10,000 Lux) - 45 hours, Outdoors, Sunny (100,000 Lux) - 8 hrs Durable, hardened non-reflective mineral crystal; Retrograde perpetual calendar function; Alarm function; Dual-time function with 24-hour subdial Brown dial; Month-day-and-date function: Day indicator between 2 and 3 o'clock, Date function at 4 o'clock; Screw-back case Water-resistant to 330 feet (100 M)