I’ve always been fascinated by calendrical systems, as it has always been basically the only way we as a civilization know how to track time. Just some of the forms that have come about over the ages:

  • Clocks
  • Wristwatches
  • Chronometers
  • Weekly, monthly, and yearly calendars
  • The different phases of the Moon, the Sun, and the four seasons
  • The changes in the paths of the stars in the sky

As you might have noticed, there is a variety of different systems. However, as far as I know, there is no system that can specifically classify these systems.

So, I thought I’d give it a go, which is what you’ll find below: the CIC Cataloguing System, or CICCS.


[A]-[B]-[C1]:[C2]:[C3] … [C𝑛]

A  = Calendar Type Identifier
B  = Calendar Subtype Identifier
C1 = 1st-Level Number Base
C2 = 2nd-Level Number Base
C3 = 3rd-Level Number Base
C𝑛 = 𝑛th Number Base

Element Descriptions

Calendar Subtype Identifier: A 4-letter abbreviation for a particular calendar type.


Calendar Subtype Identifier: A 3–10-character abbreviation for a particular variation of a calendar type. Fewer characters are better, but sometimes brevity must be sacrified for conciseness, as one will see in the first of the examples below.

(This element is optional, since not all subtypes are always known or no subtypes exist.)


1st-Level Base: The numerical base of all units directly subsequent to, and multiples of, the base unit.
2nd-Level Base: The numerical base of all next-larger units that are multiples of the 1st-Level unit(s).
3rd-Level Base: The numerical base of all next-larger units that are multiples of the 2nd-Level unit(s).
𝑛th-Level Base: Just another way of saying, “… and so on until calendar is sufficiently classified.”

Step-by-Step: ISO 8601

In the ISO 8601 form of the Gregorian Calendar, the 1st level consists of the Gregorian minute and the Gregorian hour, both of which are directly subsequent to the SI second in terms of magnitude. Thus, this latter unit is the base unit, the former units being 60× its value.

The 2nd level is the solar day, which is base-24 due to being a multiple of the 1st-level unit, the Gregorian hour.

The 3rd level is the solar year—its base is 365, due to it being a multiple of the 2nd-level unit, the solar day.

(Note: You could place the Gregorian month as the 3rd-level unit and the solar year as the 4th-level unit, but you would have to place a variation operator, i.e. plus-or-minus ( ± ), since a Gregorian month’s length is not constant. Defining the year’s base in days makes it more organized and is just as much, if not more, frequently used in day-to-day life.)

Therefore, ISO 8601’s profile would be as follows:

Calendar Type: Gregorian Calendar (GREG)
Calendar Subtype: ISO 8601 (ISO8601)
1st-Level Base: 60
2nd-Level Base: 24
3rd-Level Base: 365

Calendar Identification Code: GREG-ISO8601-60:24:365.


1 For more information on the Mayan Calendar, see this article by the Smithsonian National Museum of the American Indian.
2 Courtesy of Dr. Markus Kuhn, a University Senior Lecturer at the University of Cambridge, released under a CC BY 4.0 International license.
3 For more information on the Daisho-Reki subtype, see this article by the National Diet Library of Japan.
4 Courtesy of Utrecht University.


Image Credit:

“Calendar*”, by Dafne Cholet.
Released under a CC BY 2.0 Generic license.
Image has not been changed.
This use does not imply endorsement of the above content.


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