The Date Complication – An Unnecessary Yet Expensive Function?

The Date Complication – An Unnecessary Yet Expensive Function?

The date complication was the ideal companion for the first execution of SNGLRTY.

Time is presented in a new way; it is simple, different, and patented. Yet, with many new time displays that are launched, complexity often takes precedence over function. Some of these time displays look complicated but are easy to power with a standard movement. 

When Steve and I talked about watches that evening, that first conversation that led to SNGLRTY, we imagined the classic analog watch but with twists. A reference to the classic three-hand watch, executed as a single-hand watch with the minutes rotating anti-clockwise on a disc and a seconds hand for accuracy. The striking simplicity of SNGLRTY required the highest-quality mechanical movement, and those only come from Switzerland.

The epitome of the classic wristwatch

Part of the classic wristwatch, the epitome of a wristwatch, is the date complication that results in the date window. A white date in a rectangular window at the 3 o’clock or 6 o’clock position was necessary for SNGLRTY. It was just my opinion but when Steve and I sat down to finalize the scope for the engineers, we both agreed. Little did we know that we would end up complicating one of the classic watch complications!

The Complexity In Simplicity

Date and calendar are part of our daily life.  The display of the date on a wristwatch appears as a simple and unspectacular watch complication for that very reason. Yet, the complexity of the window date display should not be underestimated. 

The date function is most commonly driven from the minute wheel in the center of the movement. The power for the date complication must be transferred from the small-diameter wheel to a large-diameter wheel located at the edge of the movement. To achieve this, the system must overcome angular errors and the difficulties associated with advancing the date over a ten to fifteen-minute period. The date disc is also relatively heavy, and this creates additional friction that must be overcome by taking more power from the minute driver.

Thus there are many competing priorities in designing and implementing the date complication.  The actual design itself has to be as efficient as possible. Its implementation is critical and requires every component to be manufactured to very fine tolerances to reduce friction, and then the assembly has to be undertaken with extreme care.

A Brand Built On The Date Function

In the history of watches, the date and calendar complications are behind repeating strike movements, alarm clocks, and chronographs. This is not due to a lack of craftsmanship or technology. The English watchmaker Thomas Mudge designed and built the first pocket watch with a perpetual calendar as early as 1764. However, it was not until 1915 that A. Hammerly from La Chaux-de-Fonds applied for a patent for two calendar wristwatches. In both watches, the date could be read employing a center hand. In one version, the day of the week was also displayed in a small window below the 12 o’clock position. We are all very familiar with this Day-Date display that was launched in 1956 by Rolex. 

Around the same time as A. Hammerly, the watch manufacturer MOVADO came up with a digital date display.  This displays the date on a rotating ring beneath the dial, the date appearing through a window, or aperture, in the dial.

But there was always an issue with the size of the date. This was an issue that Hans Wilsdorf faced.  For the 40th birthday of his watch brand in 1945,  ROLEX launched the groundbreaking Datejust.  This watch featured a waterproof case, self-winding movement, official chronometer-certified accuracy, and just-in-time switching window date. The problem was that Wilsdorf’s wife suffered from poor eyesight and had to wear glasses to read the date. According to his widow, the ROLEX proprietor spent a lot of time in the bathroom because “that’s where he had the best ideas.” While he was in the bathroom one day, a drop of water lay precisely on the date position of his Datejust and magnified the number wonderfully. This is how the date magnifier was born.

The Knuckle Rule

Another problem is that the months are very irregular.  You may remember this from the knuckle rule when you were younger.  The months have alternating 31 and 30 days, starting in January with 31 days, but there are exceptions. February is the first exception as it has only 28 days and then, to make matters more complicated, every 4th year, in leap years, has 29 days. August, the next exception, should have 30 days according to the alternate rule, but it has 31 days. 

As children, we all struggled with remembering these rules, or perhaps we still do? Before mobile phones, the knuckle rule was a handy way to remember the number of days in each month. 

If you need a quick refresher, here is how it works. Clench your left hand into a fist and hold it in front of you so that the knuckles point upwards. The knuckles represent the months with 31 days, and the valley between the knuckles represents the months with less than 31 days. From left to right, the knuckle of the little finger represents January with 31 days, February with 28 days in the hollow, then March with 31, and so on to the knuckle of the index finger, which represents July with 31 days. Now, to continue, we move on to the right hand and clench it into a fist. Continuing from left to right, starting with the index finger’s knuckle, August has 31 days than September 30 days, and it continues until December, represented by the knuckle of the ring finger. 

Different Level of Complexity

As you can see by the Knuckle Rule’s description, putting this logic into a mechanical movement is quite the challenge. Due to these complexities, a variety of different calendar displays have been developed over the years.

1) The Simple Calendar. As the name suggests, this is the most straightforward calendar function.  When a short month is encountered, the date display must be adjusted by hand on the first day of the following month. Only between 1 July and 30 September, for 92 days, does the simple calendar display the correct date without manual intervention.

2) The Annual Calendar. The annual calendar takes the mechanical complication up a level so that the date needs to be corrected only once a year.  The movement is mechanically programmed so that only on 1 March each year (i.e., after February) does the date complication need to be adjusted.

3) The Four-Year Calendar. The four-year calendar can accommodate February with 28 days.  Only on leap years is it necessary to correct the date display. 

4) The Perpetual Calendar. The perpetual calendar is the gold standard and shows the date and the day of the week, the month, and the year. Watches with a perpetual calendar require no manual intervention, provided that the watch remains wound at all times. These little mechanical marvels can deal with leap years.  

But are they genuinely perpetual, displaying the correct date for all time? Not quite. Every year that is divisible by 100, the leap year is not observed, but to complicate matters in the year that is divisible by 400, a leap year is observed.  For example, there was a leap day in 2000, but there will be no leap day in 2100. 

So a perpetual calendar wristwatch or pocket watch needs to be adjusted once every 100 years, but every 400 years, it will still be accurate and require no adjustment. There are watches with a perpetual calendar that take the 100 rule into account and therefore do not have to be reset until 2400. Just imagine the mechanical memory required to create this logic. The gear train for the perpetual calendar is, for me, the underrated royal class in watchmaking.

What is SNGLRTY’s take?

So what does this all have to do with SNGLRTY and the development of our movement? There was no standard automatic movement available to drive the minutes counterclockwise and reduce its speed of rotation. This led us to develop a complication plate placed on a tractor movement that provides the essential timekeeping functions.

When we discussed this and set the brief for the engineers who developed the complication plate, we did not want any additional complications over and above changing the time display. We were not looking for an extra challenge for our complication plate. We desired to launch SNGLRTY with the functions of a classic watch. For us, this meant that the date complication should be available, just the simple calendar.

We Wanted The Date, But Not At The Bottom of a Well

It sounds simple; the tractor movement has a date wheel, so it is simple to have it on the SNGLRTY display.  The issue is that the SNGLRTY complication plate sits on top of the tractor movement. I did not want the date display on SNGLRTY to be buried deep under the dial and complication plate as if it was at the bottom of a well. 

So, in the briefing to the engineers, it was clear that the date had to sit on the complication plate. This stipulation meant that it was necessary to develop two complication plates, one with the date complication, the other without. 

The complication plate necessitated moving the date display from the top of the tractor movement to the top of the complication plate. There was an option to put a magnifying glass on the date aperture to magnify the date, as Rolex has done. Neither Steve nor I was comfortable with this solution, so sought a more elegant solution. 

Consequences of the Complication Plate

Whether a function is realized using a complication plate or is integrated into the movement is not apparent from the watch’s exterior. There may be small indications; perhaps an increased height of the watch case is a consequence of a complication plate. This is not visible, as it can be compensated for by choice of tractor movement and the case design. 

Another feature that can indicate a complication plate is the location of the pushers, which are on a different plane above the crown axis of the tractor movement. A good example is the famous 2025 chronograph module movement developed by Dubois Dépraz.

Another discernible detail is the date indication, which usually remains part of the base movement and lies below the dial and complication plate. The dial is between 0.40 ~ 0.60 mm, depending on how elaborate the watch is. Complication plates vary in height but often have a height of at least 1.5 mm. 

This means that if the date display is not moved onto the top of the complication plate and remains on the base movement, it will sit at least 1.9 mm below the dial surface. With the size of the date indication on the tractor movement fixed, the date appears deep in a well, small and difficult to read.

From Well Bottom to Big Date

This was not acceptable to us; we had simple time reading and wanted the date to be clear and legible.  To achieve clear and eligible reading the date had to be transferred to the top of the complication plate. The advantage of this is that it allows us to display the calendar numbers on a much larger diameter in comparison to the tractor movement. This means that numerals can be printed larger and results in a big date for SNGLRTY.

The problem is, we had decided all this without realizing the practical implications of what we were asking for. We were not aware that the standard date jump on the tractor movement was quite so complex. How we solved this and developed the date function for SNGLRTY integrated into the complication plate will be revealed in part 2.