If you have a Casio G-Shock GA-2100, Module 5611, and your Day of the week hand is incorrect or not properly aligned, you will need to do 2 things to fix it.
1, Make sure your date is correct on your watch including the month and year, as the day of the week is automatically calculated by the watch software.
2, Reset your Casio G-Shock GA-2100 watch using these steps: