Holy cow, I wrote a book!
Commenter Martin notes that
if you have multiple copies of Windows installed on your machine,
then each one will try to adjust the clock when you enter or
exit daylight saving time.
"I cannot believe that this feature is a bug.
Please could you comment this?"
This falls into a category of issue that I like to call
"So what did you expect?"
(This was the catch phrase of the old
If you have multiple operating systems installed on your machine,
each one thinks that it has control of your computer.
It's not like there's some standard cross-operating system
mechanism for negotiating control of hardware resources.
If you install CP/M and MINIX on your machine,
each one is unaware of the presence of the other.
CP/M doesn't know how to mount MINIX file systems and update
a configuration file to say "Hey, I updated the time,
you don't need to."
And not that you would expect it to, either.
It's like signing up for two housekeeping services
and telling both of them to water the plants every Monday.
And lo and behold, every Monday, the plants get double-watered.
There's no standard protocol for multiple
housekeeping services to coordinate their activities;
each housekeeping service assumes it's responsible for
cleaning your house.
Why does Windows keep your BIOS clock on local time?