Big date

A date window is the most useful thing a watch can add to the time, and for sixty years it was also the hardest thing on the dial to read. The reason is geometry. A conventional date disc carries all thirty-one numerals around one ring, so each gets a thirty-first of the circle, and the digits come out about the size of a grain of rice. The big date, or grande date, or outsize date, depending on the house, splits the number into two digits and gives each its own disc, so the numerals can be about three times as tall. It arrived on the wrist in 1994 and has been copied, varied and patented around ever since.

The idea is older than the watch. On 12 April 1841 the Dresden opera house opened with a clock above the stage that showed the hours and the minutes in five-minute steps as numerals on two drums, built in the workshop of the court clockmaker Gutkaes with his partner Ferdinand Adolph Lange. When Lange’s great-grandson Walter and Günter Blümlein refounded A. Lange & Söhne in 1990 and needed a face nobody would confuse with a Swiss one, they quoted it. The mechanism to do it on a wrist was patented through Jaeger-LeCoultre, inside Blümlein’s group, on 22 August 1991, with Roger Guignard and Blümlein himself as inventors; the Lange 1 was shown in the Dresden Residenzschloss on 24 October 1994.

The two discs do not turn together. One date wheel, advanced once a day by the going train, drives two programme wheels, and each of those drives one disc. The units ring’s programme wheel has a gap, so the ring steps every night but one; the tens cross’s programme wheel has four teeth at uneven spacing, so the cross steps on the 10th, the 20th, the 30th and at the end of the month. That last step is the clever one. On the 31st the ring is already showing 1, so at midnight it does not move at all; only the cross turns, from 3 back to the blank, and the window reads 1. There is no second “1” on the ring and nothing to catch up. The two discs sit on different planes, 0.15 mm apart on the Lange, and overlap only at the window, where the gold frame’s central bar hides the step.

It costs height and energy. Two discs, two programme wheels and their jumpers stack up: a 2001 Richemont patent criticises the 1991 design for its “stacked gear trains” and proposes a thinner version, and the first Lange calibre L901.0 is 5.9 mm thick. Moving two discs at once also takes a sharper impulse than nudging one, which is why the 1994 Lange 1 let its date creep over a few minutes around midnight and the instant jump had to wait for calibre L121.1 in 2015. And the date needs its own corrector: on the Lange 1 a pusher at ten o’clock, because turning two discs through the crown is slow.

Other houses solved the seam differently. Glashütte Original’s Panoramadatum of 1997 puts the two discs concentrically on the same plane, so there is no step to hide and the digits are separated by a line of 0.06 mm with no bar between them, and it jumps instantly and can be set backwards. Girard-Perregaux patented a transparent units disc over an opaque tens disc in 1999. Blancpain’s patent of 2008 stacks three discs, 1 to 10, 11 to 20 and 21 to 31, in one window. All of them are answers to the same constraint: thirty-one numerals do not fit in one window at a size you can read across a room.

The big date is now a signature of German watchmaking, Lange and Glashütte Original above all, and a standard option everywhere else, from Jaeger-LeCoultre’s Master Grande Date to Chopard, Zenith and H. Moser. It is a modest complication by the standards of a repeater or a perpetual calendar, but it is one of the few invented in living memory, with a patent, a date and an inventor’s name on it, and the only one with an opera house in its ancestry.

Historian’s noteLange describes the Lange 1 as the first regularly produced wristwatch with an outsize date, and this site uses the same care. There are reports of earlier two-disc dates: a GUB prototype of the mid-1960s in East German Glashütte that cycled through all thirty-nine positions and needed correcting every month, and Girard-Perregaux and Mimo watches of the 1930s and 40s with separate tens and units windows. Each rests on a single source and none has been checked against a museum or brand archive, so they are noted here and not counted. The patent is often called Lange’s first; the record shows Jaeger-LeCoultre as applicant, with a German priority of 1991.