Casio designed it's G-Shock watches to be virtually indestructible rugged timepieces that can last a lifetime. G-Shock watches bearing the module 2688 marking on the back also include Casio's Waveceptor technology. Waveceptor watches are capable of synchronizing to the proper time using a signal transmitted from Fort Collins, Colorado. Waveceptor watches synchronize automatically, so all you have to do is ensure that they have a clear view of the sky, then customize the settings to fit your schedule.
Press the button in the lower left corner of the watch until you get the timekeeping screen. The screen will display the current time in its center, and the day of the week at the top of the screen.
Hold down the button in the upper left corner of the watch until the screen begins to flash. Press the lower right and upper right buttons to scroll through city names. Continue scrolling until the watch displays the name of a city in your time zone. Press the upper left button twice to set the city.
Hold down the lower right button until the watch beeps. Place the watch on a flat surface facing a window. Leave the watch for six minutes. It will automatically set the correct time.
Place the watch on a flat surface facing a window each night to allow the watch to automatically resynchronize the time.