In watchmaking, the term "digital" does not describe an electronic circuit: it describes a way of displaying time through discrete numerals rather than hands. This distinction is fundamental, because a watch can be digital in its display and completely mechanical in its movement, or quartz-powered with analog hands. Confusing these two aspects is the most common mistake I hear customers make at the counter.
The history begins with the guichet, the French window that on 1930s Cartier Tanks showed the hour jumping and the minutes scrolling. That principle — a numbered disc advancing in increments rather than rotating continuously — is still alive in the Zeitwerk by A. Lange & Söhne, where a patented vertical clutch synchronizes hours and ten-minute increments in a single simultaneous jump, with no perceptible loss of power reserve. The energy accumulated during the previous 3600 seconds is released all at once: this is the real technical challenge of the mechanical digital display, not aesthetics.
The jump can affect minutes only (jump-minute), hours only (jumping hours), or both. In the Derby Swissonic, three concentric plastic drums manage seconds, units and tens of minutes with independent springs. In the URWERK UR-112, triangular prisms engraved with numerals and filled with Super-LumiNova rotate inside sapphire cylinders: the hours jump, the minutes advance gradually every five seconds. The central differential system converts horizontal motion into vertical — micro-mechanics of the highest level, conceptually related to airport time-and-temperature displays.
On the electronic front, Twisted Nematic LCD — developed by BBC between 1969 and 1973 — made the mass-market digital wristwatch possible. The technology was licensed to Japanese manufacturers because European production costs were unsustainable: from there emerged the consumer digital industry. Today, traditional LCDs coexist with self-emissive OLEDs (more vivid colors, true blacks) and hybrid ana-digi configurations, where hands and display share the same dial but often require separate adjustments — as in the Promaster Aqualand, a direct heir to 1980s design.
A technical variant worth mentioning is the reverse display, or negative LCD: dark background with bright numerals instead of the reverse. It changes readability in backlight conditions and the power consumption of the backlighting. I'm not aware of rigorous comparative studies on rapid reading between the two configurations under real operational conditions: this is a gap that technical literature has yet to adequately address.