The G-Shock Watch is a popular line of watches made by Casio. The watch company touts the device as a tough, waterproof time keeper for the active man. To set a G-Shock watch, you need about five minutes.
Press and hold down the A button. The A button is the top left button on the side of the watch. The seconds digits will begin to flash.
Press and hold down the B button, which is the top right button on the right side of the watch. This will reset the seconds to 00 if the seconds count is between 00 and 29 and reset the watch to 00 seconds while adding a minute when the seconds are 30 to 59.
Press and hold down the C button. The C button is the bottom left button on the side of the watch. This will change the portion of the time that you may want to change. After seconds, the hours will flash, then minutes, 12/24 hour format function, year, month and day.
Toggle back and forth between the 12 and 24-hour format by hitting the B button at the top right of the watch when you are at that portion of time-changing functionality.
Press and hold down the B button to increase any number and press and hold down the D button, which is at the bottom right, to decrease the number.
Press the A button on the top left of the watch, or leave the watch alone for a few minutes for it to return to the standard time mode.