In the beginning, we had sun dials. A stick in the sand, and a shadow that you tracked as it moved around that. Noon was really easy to see, because that is the moment the sun was directly above the stick.
Somehow, we got stuck on that idea. By the time we invented clocks, noon stayed in the top position, the moment where the day is split in two. And we ended up with two 12-hour dials, one for each half of the day.
But when you look at all 24 hours at once and split the day into day and night, this division starts looking a bit odd. Our days don’t work like that. We experience a few hours of the first dial in the morning (am) and then most of the rest of our day in the evening (pm)
In a way it would make more sense for our days to be split into a day dial and a night dial. In this case, 6 would be at the top of each clock instead of 12. And if you want to take this logic even further, since the advent of electrical lighting, we could have, say, 9 at the top and split our days into when we are generally awake and when we are asleep.
The real question, however, is why have two dials in the first place? Why not just one?
One dial for your whole day
Until recently, 24 hour dials were found only on the wrists of pilots who needed a quick way to see time zones, or submariners who could not know, deep underwater, whether it was noon or midnight. 24hour.info has more historical detail and examples.
There’s been a resurgence of interest in them lately. The dial is not too hard to get used to if you simply think of the hour hand as the sun moving across the horizon.
This brings certain advantages when applied to a calendar, which PiCal makes use of. First of all, you can see your entire day at once, not just parts of it.
It’s also, as noted by the pilots of yore, a great way to get your head around time zones.
The 24 hour dial is a very logical and useful way to see time. Our only obstacle to common usage is the historical baggage of the 12 hour dial. If we could redesign time from scratch today, this would probably be it.