Crate shahanshahi 

Shahanshahi (Imperial Iranian) calendar.

This crate is spec-first: SPEC.md defines calendar rules (SPEC_VERSION). Golden rows in data/reference-dates.json anchor tests; public APIs may still evolve before 1.0.0 (see SemVer policy in the repo changelog).

Types

• ShahanshahiDate — civil year / month / day with 1925 month lengths and Mode A leap (33-year arithmetic on the underlying Hijri Shamsi year). By default, only dates inside the documented legal Shahanshahi civil era are accepted; see that type’s docs for bounds and errors.
• GregorianDate — proleptic Gregorian anchor calendar for bidirectional conversion via Rata Die (ShahanshahiDate::to_gregorian, ShahanshahiDate::try_from_gregorian).

Features

• std (default) — std::error::Error for date errors; disable with default-features = false for #![no_std] builds (core-only algorithms and types).
• proleptic — ShahanshahiDate::try_new_proleptic validates the same calendar grid without enforcing the legal era (SPEC.md § Proleptic use).
• serde — serde Serialize / Deserialize on ShahanshahiDate and GregorianDate (optional dependency with default-features = false).
• chrono — chrono::NaiveDate conversions on GregorianDate and ShahanshahiDate (implies std).
• time — time::Date conversions on GregorianDate and ShahanshahiDate (implies std).

Structs

ChronoNaiveDateOutOfRange

The Gregorian civil date is valid for GregorianDate but cannot be represented as a chrono::NaiveDate (chrono limits the representable year range).

GregorianDate

A valid proleptic Gregorian civil date (year, month 1..=12, day consistent with month/leap rule).

ShahanshahiDate

A valid civil date in the Shahanshahi (Imperial Iranian) calendar: 1 = Farvardin … 12 = Esfand, with month lengths from the 1925 solar civil law (SPEC.md § Months). Leap Esfand uses Mode A (33-year arithmetic) on the underlying Hijri Shamsi year Y_H = Y_S − 1180.

Enums

GregorianDateError

Why a GregorianDate could not be constructed.

ShahanshahiDateError

Why a ShahanshahiDate could not be constructed.

Constants

SPEC_VERSION

Tracks which written specification version this build targets.

Functions

is_shahanshahi_leap_arithmetic

Shahanshahi leap year using Mode A (same solar year as underlying Hijri Shamsi).

is_solar_hijri_leap_arithmetic

Solar Hijri leap year per the 33-year arithmetic rule (Heydari-Malayeri / Borkowski range).

shahanshahi_to_hijri_shamsi_year

Underlying Solar Hijri year from Shahanshahi year (proleptic offset).