Hold the top-left button until the city code or time starts flashing
Use the bottom-left button to move through settings
Use the top-right and bottom-right buttons to change the flashing value
Set the correct home city first
Adjust the hour, minute, year, month, and day as needed
Press the top-left button to save and exit
If your model has a radio or Bluetooth sync feature, use that to auto-set the time
Check the manual for your exact G-Shock model if the button sequence differs