time - Why is adding a clock seen as a good UX addition in so many varying situations?

When was it decided that adding a clock was good UX for everything? Sitting here in my office, I can see a clock on my desktop, a clock on my iPod, a clock on my phone, and an actual clockwork clock on the wall.

I open my browser and plenty of websites (mostly news sites) proudly present the current time, mostly in digital, but sometimes with a fancy analog Javascript clockface. I open a few applications and the time blinks at me from the status bar.

At home, there's a clock on my TV, on my microwave, my hi-fi, my DVD player, set-top box... (please don't burgle me). Since I always unplug these things, they always blink midnight; which raises an interesting question about clocks vs eco usage guidance.

There is a clock on my car's dashboard and its radio. That's just silly, really.

There's old clocks atop spires and towers in town (fair enough, historically useful), and more, new clocks decorating half the shops and buildings closer to the ground.

Why are clocks so ubiquitous? They're certainty useful, I'm not sure they're so useful that I can turn 360 degrees and get the time 4 times to a five-minute degree of error. Do we have to keep an eye on it incase it stops? Will it start going backwards if everyone stops paying attention?

So why is adding a clock seen as a good UX addition in so many varying situations?

Answer

Many many devices use time for various functions, from recording shows on DVD, to automatically starting your coffee at a specific time, to sounding an alarm. Most devices of wildly differing types are not compatible with each other. That is to say, my phone generally doesn't talk to my coffee machine, and neither of them interface with my DVD player. As such each device has to have its own time keeping device.

Further it's worth noting that many devices that have timers/delays that aren't key to specific times will end up with clocks because adding the functionality has little extra cost. That is, if you've got a display that can show time, and an internal clock in a device that can keep time, why not go ahead and show what time it is on the display when you aren't doing "more important things".

For your car example you have two unrelated devices. If you don't have a radio that shows the time (not all of them do, though exceptions are rare) having the dashboard show the time is useful. Not all cars have dashboard clocks (though again, exceptions are rare) so having a clock on the radio is also useful. If the radio was "standard" for your car, then they would be much less likely to duplicate function ... though of course with different people designing different parts it's still a possibility.