Computer system time

[Galaxy01]

My computer's system time is slower by about a minute every 2-3 days.
Does it mean that I need to replace CMOS battery?   This PC is about 10 years old and I never changed the battery. 

The PC is set to auto sync the time, so it doesn't cause much problem.

Still advisable to replace the battery, or just leave it as it is?

[nzoomed]

The battery is likely getting a bit tired, but your computer should sync to the time server and update itself.

[Agent_24]

If it's 10 years old I'd expect the battery to be pretty close to failing. Could be why the time is drifting.