Innovative technology combines with classic sport styling to bring you the Casio Men's G-Shock Solar Atomic Watch. With helpful text lining the black resin bezel, it's easy to program handy functions like the stopwatch, countdown timer, five alarms, World Time with 31 time zones, and 12- and 24-hour formats. You'll love the convenient solar-powered battery, which can operate for up to 10 months on a full charge. A bright EL backlight automatically turns on with the movement of your wrist, and the round, black dial features clearly divided sub-dials with a wealth of information, including a day, date, and month display. With reliable shock resistant technology, a water resistant depth of 660 feet (200 meters), and the handy capacity to automatically receive official atomic time through a built-in antenna, this cutting-edge timepiece is perfect for the adventurous man. Please see page E-3 in the manual, here it states the watch would need approximately 5 minutes of exposure to bright sunlight coming in through a window and 8 hours of exposure to indoor fluorescent lighting. Please see page E-45 in the manual, the G-shock button should be pressed and held for a few seconds for the Auto EL function to be turned on. The auto light switch must be turned on ( indicated by the auto light switch-on indicator) for it to operate.Please see page E-72 in the manual for any trouble shooting instructions.