When troubleshooting a computer, when might you have to enter CMOS setup?

I have a few books about managing and maintaining a PC which I looked through many times and searched online multiple times and cannot seem to find an answer. I am looking for about 3 or 4 reasons to enter CMOS when troubleshooting.

Acai Max Cleanse

you set CMOS when you build the computer. no reason to change it until you upgrade the BIOS

if you have problems in the CMOS, it's probably the CMOS battery fading away. if the computer is 4 or more years old, it is almost assuredly the CMOS battery