The battery backup circuit in a PC is a circuit originally
in IBM AT - a legacy of that well established 1984 design
using a Motorola MC146818.

To have posted as DBLEXPOSURE has, he should have first
known about that circuit. A majority of posts in this thread
are total speculation based upon no relevant technical
knowledge. That is shameful if not irresponsible. One even
claims the OS clock causes changes in a completely different
oscillator - the CMOS date time clock. Again, one who did not
first learn basic facts. Unfortunately too many people (often
who are only programmers) somehow become experts on how
hardware works. Had he even learned a PC's BIOS, then this
would have been obvious.

DBLEXPOSURE demonstrates that many just know; cannot bother
to first learn how hardware works. It is the difference
between one who is product oriented (deals in reality) and the
antonym of a product person - the MBA. DBLEXPOSURE posted
wild speculation - even worse doing so without first reading
a previously posted and technical answer. Two problems in his
response are cited. But then he adds a third problem: learns
only half of how a CMOS date time clock works; speculates that
timing changes in the OS changes a date time clock.

First what he (and others) originally posted in response to
do_not_spam_me's original question has nothing to do with the
question asked by do_not_spam_me. Second, many of those posts
all but admit they don't know - based in wild speculation.

At least, in a later post, DBLEXPOSURE attempts to learn how
the CMOS date time clock works. But he still got it wrong.
Those applications - "Likely culprits" - will not affect the
battery backup CMOS date time clock. He should have known
that even from facts that an inquisitive user observes.

BTW, Rick Yerger also criticizes DBLEXPOSURE for not
answering the question. Rather than act product oriented,
DBLEXPOSURE replies as an MBA:
Bug Off, pedal on and get a life!
Again he demonstrates no grasp of facts - instead using
feelings as if his feelings were facts. I don't have anything
to apologize for when I criticize what DBLEXPOSURE and others
have posted. Wild speculation was misrepresented as fact -
and did not even answer do_not_spam_me's question.

Two factors cause significant variation of the CMOS date
time clock. No trimmer capacitor and a timer that varies due
to different voltages.

James Sweet wrote:
Why is speculation useless? Nobody can give one solid answer because
the problem is not identical across all computers, nor is it always
caused by one simple factor. I've learned a fair amount of
interesting things from this thread, I guess you missed all that.