Changelog

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All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[0.3.0] — 2026-04-22

Bug Fixes

  • Fixes mapping CLDR calendar types to the implementation module name.

[0.2.0] — 2026-04-16

This is the first release of Calendrical, which consolidates the ex_cldr_calendars library family into a single package built on Localize. Functionality from the following libraries has been merged in: ex_cldr_calendars, ex_cldr_calendars_persian, ex_cldr_calendars_coptic, ex_cldr_calendars_ethiopic, ex_cldr_calendars_japanese, ex_cldr_calendars_lunisolar, ex_cldr_calendars_islamic, ex_cldr_calendars_format, and ex_cldr_calendars_composite.

Added

  • Calendrical.Behaviour — a defmacro __using__ template that supplies sensible default implementations of every Calendar and Calendrical callback. Calendars use the behaviour, supply an :epoch (and any non-default options), define date_to_iso_days/3 and date_from_iso_days/1, and override only the callbacks that differ from the defaults. Every generated function is defoverridable. See guides/calendar_behaviour.md.

  • All 17 CLDR-acceptable calendar types are implemented:

  • Calendrical.Composite — a defmacro __using__ template for building composite calendars that use one base calendar before a specified date and a different calendar after. Supports any number of transitions chained together. The pre-built Calendrical.England and Calendrical.Russia modules demonstrate the historical Julian-to-Gregorian transitions.

  • Calendrical.Era — an @after_compile hook that auto-generates a Calendrical.Era.<CalendarType> module from CLDR era data. Calendars use Calendrical.Behaviour get era support for free without writing any era boundary code. ETS-based locking coordinates module creation for calendars that share a cldr_calendar_type.

  • Calendrical.localize/3 — locale-aware names for :era, :quarter, :month, :day_of_week, :days_of_week, :am_pm, and :day_periods parts of any date. Falls through to all 766+ CLDR locales available from Localize.Calendar. Handles the CLDR _yeartype_leap variant for Hebrew Adar II without needing month_patterns substitution.

  • Calendrical.strftime_options!/1 — returns a keyword list compatible with Calendar.strftime/3 so the standard library's formatter can produce locale-aware output for any Calendrical calendar.

  • Calendrical.shift_date/5 and Calendrical.shift_naive_datetime/9 — calendar-aware date/datetime shifting that supports the standard Date.shift/2 and NaiveDateTime.shift/2 APIs across every Calendrical calendar.

  • Calendrical.Interval — Date.Range for years, quarters, months, weeks, and days in any supported calendar. The Calendrical.Interval.relation/2 function implements Allen's interval algebra (precedes, meets, overlaps, contains, …).

  • Calendrical.Kday — finds the n-th occurrence of a given weekday relative to a date (e.g. "the second Tuesday in November", "the last Sunday before Christmas").

  • Calendrical.FiscalYear — pre-built fiscal calendars for 50+ territories (US, AU, UK, JP, …). The Calendrical.FiscalYear.calendar_for/1 factory creates a fiscal calendar for any supported ISO 3166 territory code.

  • Calendrical.Format and Calendrical.Formatter — calendar formatting via a behaviour-based plugin system. Includes Calendrical.Formatter.HTML.Basic, Calendrical.Formatter.HTML.Week, and Calendrical.Formatter.Markdown for rendering calendars to HTML and Markdown. Custom formatters can be added by implementing the Calendrical.Formatter behaviour.

  • Calendrical.Parse — parses ISO-8601 date and datetime strings into the calling calendar via parse_date/1, parse_naive_datetime/1, and parse_utc_datetime/1.

  • Calendrical.Preference — calendar_from_locale/1 and calendar_from_territory/1 return the preferred calendar for a CLDR locale or ISO 3166 territory.

  • Calendrical.Ecclesiastical — Reingold-style algorithms for the dates of Christian liturgical events in a given Gregorian year, organized into three traditions:

    • Western (Roman Catholic / Anglican / most Protestants, Gregorian computus, results returned as Calendrical.Gregorian dates): easter_sunday/1, good_friday/1 (two days before), pentecost/1 (49 days after), advent/1 (the Sunday closest to 30 November), christmas/1 (25 December), epiphany/1 (first Sunday after 1 January, US observance).

    • Eastern Orthodox (Julian computus, results returned as Calendrical.Julian dates so the calendar context is visible): orthodox_easter_sunday/1, orthodox_good_friday/1 (two days before), orthodox_pentecost/1 (49 days after), orthodox_advent/1 (the start of the Nativity Fast on 15 November Julian — Eastern Orthodoxy has no movable "Advent Sunday" equivalent), eastern_orthodox_christmas/1 (25 December Julian, projected onto the Gregorian calendar).

    • Astronomical (the World Council of Churches' 1997 Aleppo proposal for unifying Western and Eastern Easter; not currently used by any Church, included for comparison; year range restricted to 1000..3000): astronomical_easter_sunday/1 (first Sunday strictly after the astronomical Paschal Full Moon), astronomical_good_friday/1 (two days before), paschal_full_moon/1 (the astronomical PFM itself, computed via Astro.equinox/2 and Astro.date_time_lunar_phase_at_or_after/2).

    Plus coptic_christmas/1 (29 Koiak Coptic) which doesn't fit cleanly into any of the three traditions.

    The module's moduledoc includes a comparison table showing the three Easter computations side-by-side.

  • Eleven exception modules in lib/calendrical/exception/, one per file, modeled after the Localize convention. Each has semantic struct fields, an exception/1 constructor that takes a keyword list, and a message/1 callback that uses Gettext.dpgettext/5 for translation:

  • Calendrical.Gettext — gettext backend for the Calendrical library, using the "calendrical" domain with four contexts: "calendar", "date", "format", and "option".

  • Embedded CLDR Umm al-Qura reference data sourced from R.H. van Gent's Utrecht University dataset (1356–1500 AH), cross-referenced against the KACST published tables. The data is encoded as compile-time module attributes and consumed via O(1) and O(log n) lookup.

Changed (vs. ex_cldr_calendars)

  • All Cldr.Calendar.* module names renamed to Calendrical.*. The detailed renaming map is in guides/migration.md.

  • The :cldr_backend option and the entire backend-module architecture have been removed. Calendrical reads CLDR data directly from Localize.Calendar at runtime; no compile-time backend module is required. Functions that previously took a :backend parameter no longer accept one.

  • Error returns use the modern Elixir convention {:error, %Exception{}} instead of the legacy two-tuple form {:error, {ExceptionModule, "message"}}. Callers can pattern-match on the exception's structured data fields (e.g. %Calendrical.MissingFieldsError{function: f, fields: fs}).

  • Exception names ending in non-Error suffixes have been renamed to use the Error suffix consistently with Localize (Calendrical.MissingFields → Calendrical.MissingFieldsError, Calendrical.InvalidCalendarModule → Calendrical.InvalidCalendarModuleError, etc.).

  • Calendrical.Hebrew now uses CLDR's Tishri = 1 month numbering instead of Reingold's Nisan = 1 numbering. The previous numbering produced wrong localized month names because CLDR Hebrew data uses Tishri = 1.

  • Calendrical.shift_date/5 and Calendrical.shift_naive_datetime/9 now apply duration units in the standard order (years → months → weeks → days), matching the Elixir stdlib Date.shift/2 convention. The old Cldr.Calendar.plus(date, %Duration{}) applied units in the opposite order.

  • Calendrical.Duration has been removed. Use Elixir's built-in %Duration{} struct (since Elixir 1.17) and Date.diff/2 instead.

  • The plus/minus callbacks have been removed from the Calendrical behaviour. Calendar arithmetic is now driven exclusively by Date.shift/2 / NaiveDateTime.shift/2, which delegate to the calendar's shift_date/4, shift_time/5, and shift_naive_datetime/8 callbacks.

  • All conditional code that supported Elixir versions older than 1.17 has been removed. Calendrical now requires Elixir 1.17+ and Erlang/OTP 26+, matching Localize. Removed 24 obsolete Code.ensure_loaded? / function_exported? / Version.match? guards across 7 files.

  • Calendrical.paschal_full_moon/1 has moved to Calendrical.Ecclesiastical.paschal_full_moon/1. The new home is alongside the rest of the Christian-calendar functions.

Removed

  • Cldr.Calendar.Duration — replaced by Elixir's built-in %Duration{}.

  • The MyApp.Cldr.Calendar.* backend modules and the cldr_backend_provider/1 callback. All locale data is now read from Localize at runtime.

  • Calendrical.plus/{4,5,6}, Calendrical.minus/{4,5,6}, the plus/6 callback in Calendrical.Behaviour, and the corresponding :months clause in Calendrical.Base.Month and Calendrical.Base.Week. Use Date.shift/2 / NaiveDateTime.shift/2 instead.

  • Calendrical.Sigils (the ~d sigil). Elixir's native ~D sigil has supported a trailing calendar suffix since Elixir 1.10 and works for any module implementing the Calendar behaviour. Use ~D[2024-09-01 Calendrical.Hebrew] instead of ~d[2024-09-01 Hebrew]. The Calendrical.Sigils sigil's other features (default of Calendrical.Gregorian, ISO week-date format yyyy-Wmm-dd, fiscal calendar shortcuts, B.C.E./C.E. era markers) are minor conveniences that did not justify maintaining a parallel sigil system. See guides/migration.md for one-line equivalents of every removed feature.

Calendars

This release introduces 17 calendar implementations covering every CLDR-acceptable calendar type. See guides/calendar_summary.md for the full list grouped by family, with month structures, leap-year rules, and reference dates.