How do we tell time?

Shadows

Gravity

Pendulums

Tangible

Absolute

Singular

But all clocks need a heartbeat

Perhaps like a swinging pendulum?

Clocks with pendulums have to be wound up.
Gears in a clock are moved by the swinging pendulum.

Gears with different numbers of teeth move each "hand" a certain amount.

Do computers have a heartbeat?

Yes. A crystal oscillator or a counter circuit.

A crystal oscillator vibrates at a regular speed when connected to a power source
A counter circuit counts the number of electric oscillations coming from a power source.

Osculations are just regular pulses in electric currents.
Pulses per second are measured in hertz

60 hertz = 60 osculations per second

60 hertz = 1 second
3,600 hertz = 1 minute
216,000 hertz = 1 hour
5,184,000 hertz = 1 day

There are actually two types of clocks
in a computer.

One is a hardware clock known as
the Real Time Clock
and the other is Software Clock.

Real Time Clock the kind of clock previously described.
It is powered by a a small backup battery that runs even when the
machine is powered off.

Today, most computers set their time
using the Network Time Protocol.

Clocks synchronize between computer systems through data networks.

NTP is one of the oldest Internet protocols in current use.
NTP was designed by David L. Mills of the University of Delaware
and has been used since before 1985.

NTP is intended to synchronize all participating computers to
within a few milliseconds of Coordinated Universal Time (UTC).

This is how you computer knows to nag
you when your time and date settings are
wrong.

The computer is always right.

As for aesthetics we are mostly past the days of wooden mantel pieces.

Most websites don't bother telling you a time since
most all computer have a building in system clock.
But if you want you can get any look you want.

Ooh, like this. Just like a real clock!

Or maybe step into The Futuuure!

Maybe just make the worst clock?