G-Shock Watches are made for the most extreme environments and will take excessive abuse without failure. They are built with digital precision housed in a fortress featuring the greatest shock resistance. Casio G-Shock watches feature superior quality with the latest styling and functionality. And this may be the last watch you ever need to buy! Casio has added two high-tech innovations to this watch that make it virtually maintenance free. This watch is powered by light! That's right - light. A solar cell under the dial gathers any light, converts it to electricity and stores the energy in a rechargeable battery. You will never need to replace a battery again! And it has a built-in Power Saver function so when the watch isn't being used it goes into Sleep mode to save energy. The time is automatically calibrated to the most accurate timekeeping device in the world - the atomic clock in Fort Collins, Colorado. Once you set your home city, your watch will automatically receive a signal every night and recalibrate the time, including daylight savings time! Under good conditions, signal reception is possible within a radius of 2,000 miles of the transmitter in Ft. Collins, Colorado. In addition to this, the auto-calendar is set to automatically adjust to the correct date every month, including leap years.