Calendar designed to look up the day of the week for a given date
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Perpetual calendar" – news · newspapers · books · scholar · JSTOR(January 2012) (Learn how and when to remove this message)
Illustration from 1881 U.S. Patent 248872, for a perpetual calendar paperweight. The upper section is rotated to reveal one of seven lists of years (splitting leap years) for which the seven calendars below apply.A 50-year "pocket calendar" that is adjusted by turning the dial to place the name of the month under the current year. One can then deduce the day of the week or the date.
A perpetual calendar is a calendar valid for many years, usually designed to look up the day of the week for a given date in the past or future.
For the Gregorian and Julian calendars, a perpetual calendar typically consists of one of three general variations:
Fourteen one-year calendars, plus a table to show which one-year calendar is to be used for any given year. These one-year calendars divide evenly into two sets of seven calendars: seven for each common year (the year that does not have a February 29) with each of the seven starting on a different day of the week, and seven for each leap year, again with each one starting on a different day of the week, totaling fourteen. (See Dominical letter for one common naming scheme for the 14 calendars.)
Seven (31-day) one-month calendars (or seven each of 28–31 day month lengths, for a total of 28) and one or more tables to show which calendar is used for any given month. Some perpetual calendars' tables slide against each other so that aligning two scales with one another reveals the specific month calendar via a pointer or window mechanism.[1] The seven calendars may be combined into one, either with 13 columns of which only seven are revealed,[2][3] or with movable day-of-week names (as shown in the pocket perpetual calendar picture).
A mixture of the above two variations - a one-year calendar in which the names of the months are fixed and the days of the week and dates are shown on movable pieces which can be swapped around as necessary.[4]
Such a perpetual calendar fails to indicate the dates of moveable feasts such as Easter, which are calculated based on a combination of events in the Tropical year and lunar cycles. These issues are dealt with in great detail in computus.
An early example of a perpetual calendar for practical use is found in the Nürnberger Handschrift GNM 3227a. The calendar covers the period of 1390–1495 (on which grounds the manuscript is dated to c. 1389). For each year of this period, it lists the number of weeks between Christmas and Quinquagesima. This is the first known instance of a tabular form of perpetual calendar allowing the calculation of the moveable feasts that became popular during the 15th century.[5]
The chapel Cappella dei Mercanti, Turin contains a perpetual calendar machine made by Giovanni Plana using rotating drums.
^U.S. patent 1,042,337, "Calendar (Fred P. Gorin)".
^"Aluminum Perpetual Calendar". 17 September 2011.
^Doerfler, Ronald W (29 August 2019). "A 2010 "graphical computing" calendar". Retrieved 30 August 2019.
^Trude Ehlert, Rainer Leng, Frühe Koch- und Pulverrezepte aus der Nürnberger Handschrift GNM 3227a (um 1389); in: Medizin in Geschichte, Philologie und Ethnologie (2003), p. 291.
and 24 Related for: Perpetual calendar information
A perpetualcalendar is a calendar valid for many years, usually designed to look up the day of the week for a given date in the past or future. For the...
The Buddhist calendar is a set of lunisolar calendars primarily used in Tibet, Cambodia, Laos, Myanmar, Bangladesh, India, Sri Lanka, Thailand and Vietnam...
Gregorian calendar: Holocene calendar International Fixed Calendar (also called the International Perpetualcalendar) World Calendar World Season Calendar Leap...
wristwatch, Ref. 3414. Patek Philippe popularized complications such as perpetualcalendar, split-seconds hand, chronograph, and minute repeater in mechanical...
Historically Highly Important 18K Gold Automatic PerpetualCalendar Wristwatch With English Calendar, Leap Year Indication and "No Moon" Ref. 3448 "Alan...
complicated mechanical pocket watch displaying the Gregorian, Judaic, and lunar calendars featuring 57 complications. The watch was assembled by Vacheron Constantin...
total of 24 different functions. These included Westminster chimes, a perpetualcalendar, sunrise and sunset times, and a celestial map of New York as seen...
Such a calendar is also referred to as an observation-based calendar. The advantage of such a calendar is that it is perfectly and perpetually accurate...
A Runic calendar (also Rune staff or Runic almanac) is a perpetualcalendar, variants of which were used in Northern Europe until the 19th century. A...
complications, including a grand and small strike, minute repeater, alarm, perpetualcalendar, deadbeat seconds, chronograph with jumping seconds, and split-seconds...
article: British Calendar Act of 1751 Untangling Lady Day dating and the Julian Calendar by Erin Blake (Folger Library) The PerpetualCalendar by Toke Nørby...
and Shepard. p. 348. The PerpetualCalendar Gregorian Calendar adoption dates for many countries. What is the Gregorian calendar? with adoption dates for...
represented, and expire at the year's end. A perennial calendar differs also from a perpetualcalendar, which is a tool or reference to compute the weekdays...
after year. The World Calendar can be memorised by anyone and used similarly to a clock. Because the World Calendar is perpetual, there is no need to churn...
public transport usage. In 1930, Sidis received a patent for a rotary perpetualcalendar that took into account leap years. For this work, he was invited to...
the day of the week for a given date. It provides a perpetualcalendar because the Gregorian calendar moves in cycles of 400 years. The algorithm for mental...
clock dates from 1843. Its main features, besides the automata, are a perpetualcalendar (including a computus), an orrery (planetary dial), a display of the...
Gyrotourbillon I. Gyrotourbillon I is a double-axis tourbillon with a perpetualcalendar and equation of time, and since then, Jaeger-LeCoultre has gone on...
Giovanni Plana devised a perpetual-calendar machine, which, through a system of pulleys and cylinders, could predict the perpetualcalendar for every year from...
Dvin to establish a fixed calendar of the movable and immovable feasts of the Armenian Church. The result was a perpetualcalendar based on a 532-year cycle...
Plana devised a PerpetualCalendar machine, which, through a system of pulleys and cylinders and over, could predict the perpetualcalendar for every year...
evidence points to the calendar itself being several centuries older, created in the Iron Age. The Runic calendar is a perpetualcalendar based on the 19-year-long...
Global Information
