Why Clock Faces Use Roman Numerals

A clock is the last object in ordinary life still labelled in the numerals of ancient Rome, and the reason is not tradition for its own sake but an accident of when the dial was invented.

They were simply the numerals of that world

The first mechanical clocks in Europe appear in the late thirteenth and fourteenth centuries, in monasteries and then on town towers. They descended, conceptually, from sundials and from the marked stone and metal of inscriptions, and the numerals used on both were Roman, because those were the numerals a European mason or metalworker wrote.

Hindu-Arabic figures had arrived by then — Fibonacci's Liber Abaci set them out in 1202 — but adoption was slow and uneven, and in some places actively resisted. Florence restricted their use in commercial records in 1299, partly on the reasonable ground that a 0 or a 6 could be altered by a dishonest hand more easily than a row of tally-like strokes. For a century or more the new numerals lived in the counting house while the old ones stayed on the wall, and a clock dial was a wall.

By the time Arabic numerals had won everywhere else, the dial had already set. Later makers who wanted a clock to look like a clock reproduced what a clock looked like, which is how a design decision made by people with no alternative became a style choice made by people with plenty.

The IIII problem

Look at almost any Roman-numeral dial and the four is IIII, not IV. This is not an error and it is not rare; it is the overwhelming norm in clockmaking, and it has no agreed explanation. Several are offered, and the honest position is that none is proven.

• Visual balance. IIII sits opposite VIII across the dial, and the two heavy blocks of strokes counterweight each other; IV opposite VIII looks light. The dial also divides neatly into four numerals of I, four containing V, and four containing X. This is the most commonly repeated explanation and also the least testable.
• Casting economy. If numerals are cast in metal, using IIII means a workshop can strike a set of moulds — twenty I, four V, four X — and lay out a whole dial from them with nothing left over. Attractive, but it explains cast dials and not painted or engraved ones.
• Age of the form. Additive IIII is older than subtractive IV, which came into consistent use comparatively late. Early dials may simply have kept the numeral that inscriptions were already using.
• The Louis XIV story. The king is said to have objected to IV and ordered IIII instead. The tale is repeated everywhere and is almost certainly folklore: IIII dials are well attested long before his reign, which places the story after the fact.

A further wrinkle undercuts any tidy account. Big Ben's dial uses IV. So do a scattering of others. Whatever the rule was, it was never a rule.

What the numerals do now

Set aside history and the numerals still earn their place, for reasons about shape rather than meaning. Roman figures are built from strokes of similar weight, so a dial reads as a ring of texture rather than a set of distinct signs, and the eye takes position from the ring instead of stopping to read a number. IIII and VIII give the lower half of the dial a visual anchor that 4 and 8 do not, which is part of why a Roman dial looks settled and a numbered one looks busy.

They are also slower to read, and on a clock that is a feature. You do not read a watch face; you glance at it and take an angle. Numerals that resist quick reading push the eye back onto the hands, where the information actually is.

This is exactly why minimal faces drop them altogether. Once the hands carry the meaning, the numerals are decoration, and a designer who wants stillness removes the decoration first — leaving four marks, or twelve, or nothing but the hands against an empty field. Both choices are answering the same question about how much a face should say. One answers it with a Roman ring inherited from stonecutters. The other answers it with silence.

Bible Clock's faces come in Classic, Minimal and Sketch, each carrying its own verse, across iPhone, iPad, Mac, Windows, Apple Watch and the browser: https://apps.apple.com/us/app/verse-clock/id6783667599