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Research draft

common year

vr.tr.common-year · XCT.TME

Let an agent explain common years, relay Gregorian leap year rules, weekday patterns and calendar comparisons from calendar and astronomical sources, describe the named year types, and distinguish common years from leap years, fiscal years, the tropical year and lunar common years.

Thing Registry Cross-cutting context

Research draft, second pass

A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.

written by Claude from model knowledge without web access - no source was read, every claim is a lead to verify

Researched by: Claude

Purpose and description

Let an agent explain common years, relay Gregorian leap year rules, weekday patterns and calendar comparisons from calendar and astronomical sources, describe the named year types, and distinguish common years from leap years, fiscal years, the tropical year and lunar common years.

A calendar year that is not a leap year, having 365 days in the Gregorian calendar, 52 weeks and one day, so that it starts and ends on the same day of the week, giving seven types of common year by starting weekday, such as a common year starting and ending on Sunday; century years not divisible by 400, such as 1900 and 2100, are century common years under the Gregorian rules, and in other calendars common years differ from embolismic or intercalary years.

What it is for: Organising time in calendars.

It can be explain the rules; relay weekday patterns; describe named year types; distinguish related year concepts.

Distinguishing features

365 days

Same start and end weekday

Seven types

Century exceptions

What it looks like

Not a visible object; a calendar year.

Physical character

days: 365 count - Gregorian

leap rule: divisible by 4, except centuries not divisible by 400 note

Gregorian reform: 1582 year

common year types by weekday: 7 count

How it is recognised

Non-leap calendar year

Century common year, common year starting and ending on Sunday, Saturday, Wednesday, Friday or Tuesday

Leap years have 366 days; fiscal years follow accounting; the tropical year is astronomical; lunar calendars have different common years

Related models

is a kind of - in registry terms

calendar year

is contrasted with -

leap year

includes -

century common year

is defined by -

Gregorian calendar

In practice

Families and kinds

seven weekday types of common year

century common years

common years in lunisolar calendars

common years in the Julian calendar

Standards and regulation

ISO 8601 calendar dates

Gregorian calendar rules

Failure modes and hazards

Software bugs from wrong leap rules such as treating 1900 as leap

Confusing calendar and fiscal years

Assuming all calendars share rules

Also called

century common yearcommon year starting and ending on Sundaycommon year starting and ending on Saturdaycommon year starting and ending on Wednesdaycommon year starting and ending on Fridaycommon year starting and ending on Tuesdaycommon year starting and ending on Mondaycommon year starting and ending on Thursday

Where this came from

wikidata · CC0 1.0

Source repository Registry entry point

Drafted structure

Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.

Understand What a common year is.

Definition.

Definition

Definition.

Definition

Definition.

  1. What is a common year, and how does it differ from leap years, fiscal years, the tropical year and lunar common years? definition
  2. Is the question about a specific year, software date rules or other calendars? boundary

Types

Named types.

Types

Types.

  1. What are century common years and common years starting on each weekday? definition
  2. Which entry fits the specific year type? action
Rules Calendar rules.

Regulation.

Gregorian

Gregorian rules.

Gregorian

Gregorian.

  1. How do the Gregorian leap year rules work, and why was 2000 a leap year but 1900 not? provenance
  2. Which references are standard? provenance

Weekdays

Weekday patterns.

Weekdays

Weekdays.

  1. Why does a common year start and end on the same weekday, and how do dominical letters describe this? provenance
  2. Which sources are cited? provenance
Computing Computing.

Application.

Bugs

Date bugs.

Bugs

Bugs.

  1. What leap year bugs have affected software? provenance
  2. Which entry fits leap year problem? action

ISO

ISO weeks.

ISO

ISO.

  1. How do ISO week-numbering years relate to common years? provenance
  2. Which entry fits ISO week date? action
Context Other calendars.

Context.

Lunisolar

Lunisolar calendars.

Lunisolar

Lunisolar.

  1. How do Hebrew and Chinese calendars distinguish common and leap years? provenance
  2. Which entry fits Hebrew calendar? action

Julian

Julian calendar.

Julian

Julian.

  1. How did the Julian calendar define common years? provenance
  2. Which entry fits Julian calendar? action

What the second pass must settle

  • Should each weekday type be linked to year lists?
  • How should calendar sources be linked?
  • Should lunisolar common years be separate entries?
Draft as JSON