Why computers still struggle to tell the time

While computers manage many things with extreme precision, they have surprising difficulty keeping track of time.

It’s pretty much impossible for a computer to keep exact time, although accuracy can be improved to the extent that users are willing to spend more money on the problem, said George Neville-Neil, who spoke at the Association for Computing Machinery’s Applicative conference in New York last week.

“There are so many variables in trying to get time better or close to right,” he said.

Why computers still struggle to tell the time | PCWorld

So how does a normal wall clock do? Aren't those telling which is which? How about the digital clock?

If you computers stay within a few seconds of Window.com time I'm happy.
I check it about once a month to make sure it doesn't cause problems with Windows Updates. It's usually a few seconds difference in a month.
Other than that I don't care what day it is let alone a few seconds.