It sounds as if your BIOS settings are wrong in the CMOS area.
This is straightforward to correct.
If you say you are adjusting it each day I assume you mean via the Adjust/Date time menu on bottom right within the time display.
If so it is not modifying the CMOS.
You will have to get to that directly by shutting down your PC then restarting, pressing the Delete key (this is the usual one but check your PC manual to see if its any other, like Esc, F2, etc) during the boot process. (Tap it repeatedly once things are getting started but before the Windows screen appears)
This will take you to the BIOS menu(or directly to CMOS)
Choose the CMOS setup option.
In there you will find a field where you can type in the correct current time and date, usually based on the 24 hour clock, or with an am/pm indicator.
Okay, if the date and the time are changing this is almost certainly a sign that your CMOS battery needs changing.
Before doing this go into setup and write down your CMOS settimgs. Then replace the battery on the motherboard. Your settings may not change in this process but its better to be safe than sorry.
If the date remains fine up to the point of noon, and then just the a.m. / p.m. is off and the date gets rolled over.....I don't think it could be the CMOS battery.....It would normally forget both, and the year as well......
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