While our ancestors have long looked to the sky to determine the passing of time by observing the movements of the sun, moon, and stars, the calendar as we know it today was created in the late-16th century by Pope Gregory XIII. Our calendar—known as the Gregorian calendar—comprises 24 hour days, seven days a week, and either 28, 30, or 31 days a month for a total of 365 days a year. As the solar year is technically 365.24667 days (the time it takes the Earth to make one revolution around the sun), an extra day (29th February) is added once every four years but removed once every 100 years.
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In our fast-paced modern lives, sometimes one day seemingly blurs into the next; particularly when one doesn’t make time to observe the skies like our predecessors did. Despite the plethora of functions and aesthetics present in the watch world today, at its core, a watch is designed to tell the time. Building off that tenet, one of the most useful types of timepieces is the calendar watch. Calendar complications range from simple to, well, complicated, with both a date window and a perpetual calendar falling into the category.
Here, we unpack everything you need to know about the different types of calendar watches.
Date
The simplest form of calendar watch is a time-and-date timepiece. Though thought of as simple, the date function is technically considered a complication. Date watches feature an aperture in the dial which displays the date (often at 3 or 6 o’clock). Beneath this aperture sits a 31-day disc that makes a full rotation every 31 days. Months with less than 31 days are not taken into account, so the date function will need to be manually reset at the beginning of the next month. For example, as November only has 30 days, the date function will need to be manually moved on the 1st of December.
As one of the easiest watchmaking complications to execute, almost all watch brands have a date watch in their lineup.
A variation of the date watch is the large date; a signature for German manufacture A Lange & Söhne. The A Lange & Söhne Lange 1 and Saxonia ranges both feature the oversized date window. These large date windows show the date in two separate (but connected) windows, with the movement using overlapping or parallel discs rather than the standard 31-day disc.
Day-Date
Going a step further than displaying the date alone, day-date watches also add the day into the mix. These watches feature two apertures, one for the date and the other for the day. The mechanism behind the day-date movement is similar to that of the date, with a disc that completes a full revolution every seven days. The Rolex Day-Date (it’s in the name) is the most iconic example of this type of calendar watch. The seminal timepiece made its debut in 1956 and was the first watch to display the date and the day spelled out in its entirety.
Triple Calendar
The triple calendar expands upon the day-date, adding a month of the year aperture into the mix.
Complete calendar
A complete, or full, calendar watch displays not only the date, day of the week, and month, but also has a moonphase indicator. This information can be conveyed via standard apertures, however more complicated watches may make use of jumping or retrograde complications.
Jaeger-LeCoultre was renowned for its triple calendar watches in the mid-1900s. This heritage continues in the Swiss manufacture’s current Master Control Calendar line.
Annual calendar
Annual calendar watches represent a step up from simple date functions, thanks to their ability to account for the different days in the months with 30 and 31 days. The exception is the shorter month of February, meaning that come the 1st of March, the wearer will need to make a single (annual) adjustment.
An atypical take on the annual calendar is the Rolex Sky-Dweller, which challenges conceptions of what the style should look like. The Sky-Dweller features a patented mechanism that sees the months of the year shown in 12 apertures around the circumference of the dial, next to the hour indices, with the current month displayed in red.
More conventionally styled annual calendar watches include the A. Lange & Söhne 1815 Annual Calendar and IWC Portugieser Annual Calendar.
Annual calendars can be thought of as a bridge between simple date watches and perpetual calendar watches.
Quadrennial calendar
Also known as a semi-perpetual or four-year calendar, the quadrennial calendar is a step up from the annual calendar in that it’s able to account for not only the different days in the months with 30 and 31 days, but also the shorter month of February. However, it does not take leap years into account (i.e. when there is a 29th of February), meaning it will have to be manually adjusted every four years.
Perpetual calendar
Ah, the granddaddy of calendar watches. Perpetual calendar complications, also known as quantième perpétuel, are able to accurately keep track of the day, date, and month until the year 2100. This is because the leap year that typically occurs every four years will be skipped, meaning an adjustment on the 1st of March, 2100 is required. Someone tell my grandson.
Watches with perpetual calendar complications are able to account for the differences in days of the month including the shorter month of February) and also feature a leap year indicator which makes it easy to distinguish them from annual calendar watches. Perpetual calendar watches often also feature moonphase displays.
A feat of mechanical excellence, perpetual calendar watches represent a display of watchmaking virtuosity and are only able to be executed by master watchmakers.
An important note: when we talk about calendar watches keeping track of the date and time; this is only applicable if the watch is consistently kept wound. If the power reserve is exhausted and the watch stops running, the calendar will have to be reset. It’s a good idea to keep your watch running — perpetual calendar watches in particular are so complicated that they often require the assistance of a watchmaker to reset.
Enjoyed this article? Why not check out our Ultimate Guide To Watches here; covering everything from the anatomy of a watch to watch styles and complications.
Words by Henry Blake
