I'm slowly parting with some of my collection and have some 486 boards listed for sale elsewhere.

Someone asked if a particular board kept CMOS settings when powered off.

The board had a leaked NiCad battery and some destroyed keyboard traces, I repaired those and everything seemed to be working fine. I tried an external battery on the Ext. Bat header and it kept the CMOS settings from yesterday when I powered it off and unplugged it, it also kept the date and time from yesterday but it did not advance. Meaning the date and time were from when I shut it off, weird no?

What would cause that?