Hindu calendar
Enable an AI agent to identify a Hindu calendrical tradition, interpret its dates, assess the evidence behind calculations, and determine when conversion or observance advice is justified.
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.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an AI agent to identify a Hindu calendrical tradition, interpret its dates, assess the evidence behind calculations, and determine when conversion or observance advice is justified.
The Hindu calendar is a family of traditional Indian calendrical systems, principally lunisolar and solar, that organize dates and religious observances through rules relating lunar phases, the Sun's apparent motion and locally transmitted calendrical conventions.
It can be Identify the tradition and missing context behind a supplied Hindu calendar date.; Explain a date's year, month, fortnight, tithi, and other applicable components.; Convert a sufficiently specified date to candidate civil dates or time intervals while preserving ambiguity.; Generate or compare panchanga components for a stated locality and calculation method.; Evaluate a documented observance rule and explain why competing calendars assign different dates.; Flag unsupported historical conversions, boundary-sensitive results, and unresolved authority conflicts..
Distinguishing features
A usable instance identifies a particular tradition and rule set; the label Hindu calendar alone does not determine a unique date conversion.
Solar and lunisolar implementations must be distinguished before interpreting month boundaries or year structure.
A tithi denotes a lunar phase interval and must not automatically be treated as a midnight-to-midnight civil day.
Month names and year numbers require a month convention, era, and year-start rule before dates can be compared.
An astronomical transition, its assignment to a local calendar day, and a festival's observance date are separate determinations.
Scope
+ Identification of regional, religious, and computational calendar traditions
+ Solar and lunisolar year, month, and date structures
+ Panchanga elements and their assignment to local dates
+ Epochs, year numbering, intercalation, and exceptional date sequences
+ Location-dependent date conversion and calendrical observance rules
+ Evidence, authority, and uncertainty attached to calendar implementations
- Hinduism as a religion and its complete doctrinal or ritual systems
- Astrological predictions and interpretations of personal destiny
- Astronomy as an independent scientific discipline
- The Indian national civil calendar as a separately governed calendar system
- Almanac publications as physical or digital publishing products
- Festival narratives, ritual procedures, and administrative holiday declarations
Characteristics
- Calendar tradition
- Named regional, community, or institutional tradition; unresolved if unspecified Selects the conventions that make dates and observances interpretable.
- Calendar basis
- Solar or lunisolar, with any supplementary lunar or solar reckoning identified Determines how months and years are constructed.
- Lunar month convention
- Amanta, purnimanta, another documented convention, not applicable, or unresolved Prevents a lunar phase or fortnight from being assigned an incorrect month label.
- Era and year-start convention
- Reference to a named era, its epoch, numbering convention, and year boundary A year number is ambiguous without the rules that give it meaning.
- Reference locality
- Place with latitude and longitude in degrees, elevation where relevant, and applicable time standard Local sunrise and other reference events can affect date and observance assignments.
- Astronomical calculation convention
- Named method, parameters, reference system, and version; ayanamsha where applicable Different computational conventions can place transitions at different times.
- Panchanga components
- Tithi, vara, nakshatra, yoga, and karana, with labels and validity intervals Records the calendrical components without conflating their different boundaries.
- Month adjustment status
- Ordinary, adhika, kshaya-related, not applicable, or unresolved under the selected rules Exceptional month structures affect naming, sequence, and conversion.
- Transition instant
- Timestamp with time scale, precision, and uncertainty Supports boundary-sensitive decisions and comparison between calculations.
- Interpretation status
- Fully specified, ambiguous, disputed, unsupported, or outside validated range Determines whether an agent can return one answer, present alternatives, or request missing context.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 17 findings · 31 questions.
Tradition and calendar identity Establishes which Hindu calendrical system is being represented and how its names are used.
The registry entry covers a family of systems whose differences must remain explicit within one model.
Tradition profile
Identifies the community, region, and calendar basis relevant to an interpretation.
Identify the operative tradition
Record a named tradition and its solar or lunisolar basis before applying date rules.
- Which regional or community tradition does this calendar instance implement, and what source identifies it? provenance
- Does this implementation use solar months, lunisolar months, or different reckonings for different purposes? definition
Terminology and neighbouring systems
Separates equivalent labels from substantive differences in calendrical rules.
Resolve labels without collapsing rules
Associate language-specific names and transliterations with their meanings while distinguishing separately governed calendars.
- Which month and panchanga labels are translations or transliterations, and which indicate different conventions? definition
- What distinguishes this instance from the Indian national civil calendar or another neighbouring calendar that shares terminology? boundary
Years, months, and adjustments Describes the rules that construct and name years and months.
Date labels cannot be interpreted reliably from familiar month names or era numbers alone.
Era and year boundaries
Connects year labels to an epoch, counting convention, and calendar boundary.
Interpret the year label
Keep the era and year-start convention explicit, including named year cycles where used.
- Which era and epoch govern the year number, and how are years counted? definition
- At what calendrical event does the year change, and how are any cyclical year names related to that numbering? boundary
Month construction
Defines month boundaries, naming rules, and adjustments to the month sequence.
Derive the month sequence
Record the solar or lunar boundary convention and the rules for ordinary and exceptional months.
- Which events define a month, and how do amanta or purnimanta conventions affect its name where applicable? definition
- Under what documented conditions are adhika or kshaya-related month adjustments recognized and labelled? boundary
- How should an agent distinguish an ordinary month from another occurrence bearing the same month name? action
Panchanga and local day Represents calendrical components as intervals and explains their assignment to local days.
Panchanga transitions and civil day boundaries need not coincide, making locality and assignment rules essential.
Component intervals
Defines the five panchanga elements and the transitions relevant to each.
Record component boundaries
Represent tithi, vara, nakshatra, yoga, and karana according to their own rules rather than one shared daily timestamp.
- How does the selected tradition define and label each of the five panchanga elements? definition
- What are each component's start and end instants, and in which time scale are they expressed? measurement
Day assignment
Relates component intervals to sunrise, other reference events, and civil date labels.
Assign tithi to a local date
Make the reference event explicit and preserve cases where a tithi spans successive reference events or none.
- Which locality and reference event determine the tithi displayed for a calendar day? boundary
- How are tithis that span two successive daily reference events or occur between them represented? action
- What rule applies when the expected reference event, such as sunrise, is unavailable at the selected location? boundary
Calculation and conversion Makes computed dates reproducible and defines the limits of conversion.
A plausible date is insufficient unless its assumptions, method, and ambiguity can be inspected.
Computational conventions
Identifies the astronomical method and parameters used to calculate calendar transitions.
Declare the calculation basis
Record the computational tradition, astronomical inputs, and relevant reference-frame choices.
- Which documented algorithm, tables, or ephemeris produced the calendar, and which version was used? provenance
- Which longitude conventions, ayanamsha where applicable, and time assumptions affect the calculated boundaries? measurement
Conversion validity
Specifies what a conversion can resolve and when multiple answers or an explicit limitation are required.
Preserve conversion ambiguity
Return a point, interval, or set of candidate civil dates according to the supplied information and supported historical range.
- Are the tradition, era, month convention, adjustment status, locality, and target civil calendar sufficiently specified? boundary
- Should conversion return one civil date, multiple candidates, or a time interval for the supplied date expression? action
- For which historical periods has this implementation been checked against evidence, and where is it only a backward projection of selected rules? provenance
Observance rules and authority Connects calendar calculations to documented observance decisions and their sources.
Astronomical agreement alone does not settle a festival date when communities apply different selection rules.
Observance date selection
Records the calendrical conditions that select an observance day without modelling the ritual itself.
Apply an observance selection rule
Link the required tithi or other components to the relevant time window and precedence rules.
- Which component must prevail at which reference event or time window for this observance? definition
- What documented precedence rule resolves cases in which two days qualify or no day satisfies the usual condition? action
Authority and disagreement
Preserves the scope and provenance of competing calendar determinations.
Trace and explain date disagreement
Attribute each result to its source and distinguish computational differences from different observance conventions.
- Which almanac, institution, text, or community authority supports this determination, for which locality and year? provenance
- Does a disagreement arise from astronomical calculation, locality, month naming, or an observance selection rule? boundary
- When sources disagree, should the agent present attributed alternatives or apply a user-specified authority? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- This entry covers a family of calendar systems, not a discipline or one universally standardized calendar.
- Regional classifications are broad generalizations; precise dates require the specific calendar, locality, era and calculation tradition.
- No sources were consulted; numerical values are recalled approximations or conventional angular divisions.
- Which of these check these first hold for the sense of Hindu calendar this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Amanta lunisolar calendars, whose months end at new moon
- Purnimanta lunisolar calendars, whose months end at full moon
- Solar calendars, whose months follow the Sun's passage through zodiacal signs
- Which of these kinds and varieties hold for the sense of Hindu calendar this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Determining dates of Hindu festivals, fasts and rituals
- Preparing panchangas, traditional almanacs of calendrical and astronomical information
- Selecting auspicious times for ceremonies
- Recording and interpreting dates in historical documents and inscriptions
- Organizing regional new-year celebrations and seasonal observances
- Which of these real-world use hold for the sense of Hindu calendar this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Tithi, or lunar day - Each spans 12 degrees of increase in Moon-Sun elongation; its elapsed duration varies - degree
- Mean synodic lunar month - Approximately 29.53 - day
- Lunar months in a lunisolar year - Usually 12; 13 when an intercalary month is included - month
- Nakshatra sector in the common equal-division scheme - 13 degrees 20 minutes, giving 27 sectors around the ecliptic - angular degree
- Which of these typical measurements hold for the sense of Hindu calendar this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Treating the Hindu calendar as one uniform system produces incorrect date conversions.
- Converting a historical date without identifying its era, regional calendar and month convention can yield an incorrect year or day.
- A tithi is not a fixed 24-hour civil day; it may be absent at sunrise or occur at two successive sunrises.
- Festival dates can differ with location, astronomical calculation and rules about which tithi must prevail at a specified time.
- Ignoring intercalary months, rare omitted months or differing solar reference conventions can corrupt calendar calculations.
- Which of these failure modes and hazards hold for the sense of Hindu calendar this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Amanta month reckoning is widespread in western and southern India, while purnimanta reckoning is widespread in northern India; local exceptions matter.
- Tamil and Malayalam traditions prominently use solar calendars, while many other Hindu traditions use lunisolar calendars.
- Era numbering, year beginnings, month names and observance rules vary among regions and communities.
- Which of these regional variation hold for the sense of Hindu calendar this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- Indian national calendar - The standardized Saka-based civil calendar is distinct from the diverse traditional calendars used for Hindu observances.
- Panchanga - A panchanga is an almanac presenting calendrical elements and related information; a calendar is the underlying system for organizing dates.
- Jyotisha - Jyotisha is a broader tradition encompassing astral knowledge and astrology; Hindu calendars are systems of time reckoning informed by parts of that tradition.
- Gregorian calendar - The Gregorian calendar uses fixed month lengths and leap-year rules to approximate the tropical year, whereas Hindu calendars employ differing solar or lunisolar astronomical conventions.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of Hindu calendar this model covers, and on what evidence? provenance
What the second pass must settle
- Which regional and community traditions must be researched first to represent the registry entry's breadth without treating one implementation as universal?
- Which primary sources establish the exact month adjustment, year-start, and observance rules for each included tradition?
- Which astronomical methods and parameter choices are used by the selected calendar authorities, and how large are their boundary differences?
- What historical evidence supports conversions across changes in local calendar practice, era usage, and civil timekeeping?
- Which authorities document rules for diaspora locations, absent sunrise, and disputes over observance dates?