year
Let an agent handle years by definition (calendar, tropical, fiscal, academic), calendar system and numbering, and avoid errors from mismatched year definitions.
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 handle years by definition (calendar, tropical, fiscal, academic), calendar system and numbering, and avoid errors from mismatched year definitions.
The time the Earth takes to orbit the Sun, about 365.24 days, and the calendar unit of 365 or 366 days based on it; also used for other year definitions such as school or fiscal years.
What it is for: Organising time into seasons and annual cycles for law, business, education and culture.
It can be count and number years, in a calendar era; define custom years, such as fiscal or academic; convert between calendars; account for leap years.
Distinguishing features
Several definitions: tropical, sidereal, calendar, fiscal, academic
Calendar years depend on the calendar system
Leap years keep the calendar aligned with seasons
Some systems name years instead of numbering them
What it looks like
Not a thing to see; shown as a number (2026), a label (FY2026/27) or a name in some calendars (such as Yang Metal Dragon in the Chinese cycle).
Physical character
tropical year: 365.2422 days
Gregorian calendar year: 365 or 366 days
Julian year (astronomy): 365.25 days - used for light years
How it is recognised
Four-digit year numbers in the Gregorian calendar
Fiscal and academic year labels spanning two calendar years
Names in cyclical calendars
Related models
is made of - 365 or 366 days
is part of - calendar system
is confused with - business and government years differ
names - the year component of dates
In practice
Families and kinds
calendar year
tropical and sidereal year
fiscal year
academic or school year
leap year, even and odd years, century years
commemorative years
Identifiers
ISO 8601 year YYYY with extended forms for years outside 0000-9999
Standards and regulation
ISO 8601
National laws defining fiscal years
IAU definitions of Julian year
Failure modes and hazards
Mixing calendar and fiscal years
Leap year bugs such as 29 February handling
Year 2038 and similar overflow limits in software
Converting historical years across calendar reforms
Also called
+88
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.year-2
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 4 bundles · 8 layers · 8 findings · 16 questions.
Definition Which year.
Year definitions differ; the definition must be explicit.
Kind
Calendar, fiscal, academic, astronomical.
Year kind
The kind of year.
- Which kind of year is meant here? definition
- When does it start and end? boundary
Calendar
Gregorian or other.
Calendar
The calendar used.
- In which calendar is this year counted? definition
- What is its Gregorian equivalent? measurement
Length Days in the year.
Leap rules matter for calculations.
Leap years
Rules.
Leap rule
The leap rule.
- Is this a leap year under the applicable rule? measurement
- How is 29 February handled in this system? boundary
Duration
Astronomical lengths.
Duration
Which length is used.
- Which year length does this calculation assume? definition
- How much error does that introduce? measurement
Numbering Eras and names.
Years are numbered or named differently across cultures.
Era
CE, AH, other eras.
Era
The era and numbering.
- In which era is the year numbered? definition
- Is there a year zero in this system? boundary
Names
Cyclical names.
Year names
Names in cyclical calendars.
- What is the name of this year in the relevant cyclical calendar? definition
- When does that year begin? measurement
Use Years in law, business and software.
Year boundaries drive deadlines, accounts and software behaviour.
Fiscal and academic years
Institutional years.
Institutional year
The institutional year definition.
- Which fiscal or academic year applies, and how is it labelled? definition
- Who defines it? provenance
Software limits
Date limits and bugs.
Software limits
Known year-related limits.
- Does the system handle leap years and dates beyond 2038 correctly? boundary
- How is the year stored? definition
What the second pass must settle
- Should each kind of year be a separate entry?
- How should fiscal years be recorded per organisation and country?
- How should cyclical year names be linked to numbers?