Right on Time

Emilie Yabut-razon

t the stroke of midnight, the date and day appear simultaneously in the two windows on the dial of the Rolex Oyster Perpetual Day-date. When the watch was launched in 1956, this instantaneous simultaneous jump was a world first for wristwatches. Dubbed the “miracle at midnight,” the Rolex was the first model to spell the day of the week in full, clearly legible at 12 o’clock and available in 26 languages. The simultaneous changing of the date indication, required a mechanism of sufficient accuracy and energy to move both the day and date discs at precisely the same moment, but with an effective brake to ensure they only advanced a day at a time.

The movement required two aluminium discs, one above the other, the lower disc for the date and the upper for the day. With 31 and seven teeth respectively, the discs were driven at their centre by two independent, star-shaped wheels connected to snail cams that accumulated energy as they turned during a 24-hour period. At midnight, the cams’ energy was released and gave the corresponding tooth the impulse needed to push its star and, in turn, the disc. This ingenious engineering feat, which was then covered by four patents, also offered the advantage of spreading energy consumption evenly over a complete 24-hour cycle. This effectively preserved the precision of the certified chronometer’s movement.

Almost six decades later, Rolex has introduced a new generation of its Day-date watches equipped with the same mechanism, but it’s been optimised to take timekeeping performance to a new level. The new calibres offer up to 50 per cent more reserve power, a 15 per cent improvement in efficiency, and are tested to a higher degree than a chronometer certified by the Swiss Official Chronometer Testing Institute (COSC).

The latest models of the Day-date and