The functions of mechanical watches are varied, and different brands and types of watches have their unique designs, such as chronograph, retrograde, flyback, moon phase, minute repeater, tourbillon, and perpetual calendar.
Watch enthusiasts must have heard of affordable perpetual calendar watches. Among them, the minute repeater, tourbillon, and perpetual calendar are known as the "three major complex functions" in mechanical watches, showcasing the exquisite craftsmanship of watchmaking technology.
Although the name of the affordable perpetual calendar watches translates to "perpetual," in reality, it is closer to a "leap-year calendar." To understand the working principle of an affordable perpetual calendar watch, one must first understand the history of the Gregorian calendar. The commonly used Gregorian calendar was promulgated by Pope Gregory XIII in 1582 as the "Gregorian Calendar."
Why was the calendar reformed in 1582? Since the implementation of the Julian calendar in the Roman era until 1582, the solar year's trajectory and the actual calendar had a discrepancy of more than ten days, seriously affecting people's accurate grasp of dates, especially important holidays such as Easter.
To solve this problem, after 1582, standard Gregorian calendar rules were set: a century year must be divisible by 400 to be a leap year, for instance, the years 1600 and 2000 are leap years. However, the years 1700 and 2100 are not leap years. As this calendar is more scientific, it was accepted by many countries and regions, forming a unified standard and rule.
Understanding the difference between leap years and non-leap years makes it easier to understand the working principle of an affordable perpetual calendar watch. The affordable perpetual calendar watch operates in a complete cycle of 400 years.
Typically, watches with perpetual calendar functions use a design where every four years is a leap year, achieved by placing four years of months on a gear, eliminating the need for manual adjustment to realize the perpetual calendar function. In the past 2000 years, this design has never encountered a problem. However, as we approach the year 2100, which is not a complete cycle, watches with perpetual calendar functions will require recalibration at the manufacturer.
Affordable perpetual calendar watches not only display hours, minutes, and seconds but also have the functions to display the date, week, month, and leap year. With 24 hours equaling one day, the ratio between the hour wheel and the date wheel should be 24:1. However, in conventional watches, the hour hand makes two rotations each day. Therefore, affordable perpetual calendar watches add an intermediate wheel to adjust this difference, making the ratio between the hour wheel and the date wheel 12:1.
The core of the affordable perpetual calendar watch is a gear that completes a full rotation in four years. This gear is responsible for driving the month change and indicating the leap year.
Generally, it uses the indication method of "L (leap year), 1, 2, 3," with one full rotation equating to 48 months. The gear's grooves have four depths, representing 31, 30, 29, and 28 days. Through a set of positioning switching systems, the date jumps to the next month at the end of the month.
The positioning lever commands the actions of "jumping from the 28th to the 1st," "jumping from the 29th to the 1st," "jumping from the 30th to the 1st," and "jumping from the 31st to the 1st," four types of end-of-the-month date jumps and month changes. This is the basic operating theory of the affordable perpetual calendar watch. Do you understand?
If you are interested in watches with perpetual calendar functions, you might want to consult Shenzhen Shijin Watch Co., Ltd. They have many options, and there is always one that suits you.