PC clocks are inaccurate to save money
Quartz crystals are good at doing about 1 to 40MHz. PC clocks go at 32KHz to reduce power and hence the cost of the backup battery. The frequency of quartz crystals varies with temperature, some more than others. You get what you pay for. The crystal circuit also includes the PCB, a few capacitors an a chip. Variations in these components add a small error to frequency. Many years ago, that was fixed by adding a small variable capacitor, but that costs some money to add, and more to set correctly.
If you want you PC to know the right time, use some network time protocol software.
Still looking for a clock that reads either: "Yes, there is time." or "No, there isn't."