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Astro version 2.1.0

This is the changelog for Astro version 2.1.0 released on April 7th, 2026. For older changelogs please consult the release tag on GitHub

Bug Fixes

  • Fix application startup when neither :tz nor :tzdata is configured. Astro.default_options/0 now falls back to time_zone_database: nil instead of raising CondClauseError. Calls that do not require a time zone database (e.g. time_zone: :utc) now work without any time zone library installed.

  • Fix Astro.Supervisor.start_link/2 to gracefully handle the case where :tz_world is not installed. Previously the supervisor unconditionally referenced TzWorld.Backend.DetsWithIndexCache and crashed at startup when the optional dependency was missing.

Enhancements

  • Add Astro.new_visible_crescent/3 to predict the visibility of the new crescent moon at a given location on a given date. Three published criteria are supported via the method argument:

    • :odeh (default) — Odeh (2006) empirical criterion based on 737 observations using topocentric ARCV and a Danjon limit of 6.4°.

    • :yallop — Yallop (1997) empirical criterion based on 295 observations using geocentric ARCV.

    • :schaefer — Schaefer (1988/2000) physics-based model computing the contrast between crescent brightness and twilight sky brightness against the human contrast detection threshold.

  • Add Astro.new_visible_crescent/4 accepting atmospheric options for the Schaefer method (:extinction parameter).

  • Add Astro.Ephemeris.Downloader which automatically downloads the JPL DE440s ephemeris file (~32 MB) from NASA NAIF on first application start and caches it under the user cache directory. The download URL and cache path can be overridden with the :ephemeris_url and :ephemeris application environment keys. If the download fails, Astro.Application.start/2 now returns a clear error message explaining how to install the file manually.

Astro version 2.0.0

This is the changelog for Astro version 2.0.0 released on March 14th, 2026. For older changelogs please consult the release tag on GitHub

Breaking changes

  • Rename Astro.Solar.solar_longitude/1 to Astro.Solar.solar_ecliptic_longitude/1 and Astro.Lunar.lunar_longitude/1 to Astro.Lunar.lunar_ecliptic_longitude/1 to use unambiguous astronomical terminology.

  • Rename Astro.Lunar.new_moon/0 to Astro.Lunar.new_moon_phase/0, Astro.Lunar.full_moon/0 to Astro.Lunar.full_moon_phase/0, Astro.Lunar.first_quarter/0 to Astro.Lunar.first_quarter_phase/0, and Astro.Lunar.last_quarter/0 to Astro.Lunar.last_quarter_phase/0 to clarify that these return phase angle constants.

  • Rename Astro.Time.utc_datetime_from_terrestrial_datetime/1 to Astro.Time.utc_datetime_from_dynamical_datetime/1 to reflect the standard "dynamical time" terminology used in modern astronomical references.

  • Rename functions in Astro.Time that had names including "datetime" and consistently use the form "date_time".

  • Astro.Time.offset_for_zone/2 now returns {:ok, offset} or raises if there is an error resolving an offset. That can happen if the time zone is unknown, if there is no time in the zone or if the result is ambiguous due to DST shift.

  • Astro.obliquity/0 now returns its value in degrees (was previously radians). The only impact is to code that directly calls this function.

  • Astro.Earth.nutation/1 now returns a 3-tuple {nutation_in_longitude, nutation_in_obliquity, obliquity} instead of a single scalar value. The first element in the tuple has the same purpose as the return value of the original function. However its value may be slightly different due to the new underlying algorithms.

  • Astro.moon_position_at/1 now returns distance to the Moon in kilometres instead of metres.

  • Astro.sunrise/3 and Astro.sunset/3 now delegate to Astro.Solar.SunRiseSet which computes solar positions from the JPL DE440s numerical ephemeris rather than the previous NOAA/Meeus analytical polynomial series, and uses a scan-and-bisect solver rather than the previous iterative analytical formula.

  • Improved ΔT (delta-T) computation now uses variable ΔT based on IERS observations (1972–2025) and Meeus polynomial approximations for historical dates, replacing the previous fixed ΔT value. This improves the accuracy of all astronomical calculations but changes computed times for equinoxes, solstices, new moons, and lunar phases by up to ~22 seconds compared to version 1.x.

  • Sunrise/sunset and moonrise/moonset bisection tolerance tightened from 1.0 second to 0.01 seconds, yielding sub-second precision.

  • Remove Astro.Solar.sun_rise_or_set/3 and Astro.Solar.utc_sun_position/4 (the old NOAA/Meeus sunrise/sunset implementation). These functions were previously @doc false and are superseded by Astro.Solar.SunRiseSet.

Enhancements

Astro version 1.1.2

This is the changelog for Astro version 1.1.2 released on September 9th, 2025. For older changelogs please consult the release tag on GitHub

Bug Fixes

  • Fix Astro.sunrise/3 and Astro.sunset/3 when the resolved UTC datetime is ambiguous or has a gap (typically during a daylight savings transition). Thanks to @andykent for the PR. Closes #6 and #7.

Astro version 1.1.1

This is the changelog for Astro version 1.1.1 released on June 21st, 2024. For older changelogs please consult the release tag on GitHub

Bug Fixes

  • Remove :hackney and :tzdata from :extra_applications.

Astro version 1.1.0

This is the changelog for Astro version 1.1.0 released on June 18th, 2024. For older changelogs please consult the release tag on GitHub

Breaking Change

  • :tz_world is no longer a required dependency - it is now an optional dependency. This library is used to resolve a time zone name from a given latitude and longitude. When configured, it becomes the default method of resolving time zone names from a location. However it is no possible to provide alternative implementations for this resolution using the :time_zone_resolver option.

  • To retain the previous behaviour, applications should add {:tz_world, "~> 1.0"} to their dependencies.

Enhancements

  • Adds an option :time_zone_resolver to Astro.sunrise/3 and Astro.sunset/3 that is a 1-arity function that is invoked to resolve the time zone name from a given latitude and longitude. The default is to use TzWorld.timezone_at/1 if TzWorld is configured, otherwise an error is returned.

  • The default time zone database is now detected in the following order:

    1. Application.get_env(:elixir, :time_zone_database)
    2. TzData.TimeZoneDatabase if TzData is configured
    3. Tz.TimeZoneDatabase if Tz is configured

Astro version 1.0.2

This is the changelog for Astro version 1.0.2 released on May 27th, 2024. For older changelogs please consult the release tag on GitHub

Bug Fixes

  • Fix sunrise/sunset calculations when the solar elevation isn't 90 degrees. Thanks to @cloud8421 for the issue. Closes #5.

Astro version 1.0.1

This is the changelog for Astro version 1.0.1 released on April 6th, 2024. For older changelogs please consult the release tag on GitHub

Bug Fixes

  • Use only the configured time zone database to resolve time zone information. Therefore any module that implements the Calendar.TimeZoneDatabase behaviour can be used. This also makes the code align with the README so that either Tzdata or Tz can be configured as the systems time zone database (or any future library). Thanks to @ericlathrop for the issue. Closes #4.

Astro version 1.0.0

This is the changelog for Astro version 1.0.0 released on December 29th, 2022. For older changelogs please consult the release tag on GitHub

Enhancements

  • Release 1.0. This library was started four years ago and the public API has been stable for at least three of those years.

  • Adds Astro.sun_azimuth_altitude/2. Thanks to @kimlai for the suggestion. Closes #3.

Astro version 0.10.0

This is the changelog for Astro version 0.10.0 released on November 7th, 2022. For older changelogs please consult the release tag on GitHub

Enhancements

  • Adds Astro.Math.floor/1 and Astro.Math.ceil/1 which are needed to support Tempo.

Astro version 0.9.2

This is the changelog for Astro version 0.9.2 released on September 1st, 2022. For older changelogs please consult the release tag on GitHub

Bug Fixes

  • Update :tz_world to "~> 1.0" which will also remove Elixir 1.14 warnings

Astro version 0.9.1

This is the changelog for Astro version 0.9.1 released on October 23rd, 2021. For older changelogs please consult the release tag on GitHub

Bug Fixes

  • Ensure that gregorian_seconds is an integer before passing it to Tzdata.periods_for_time/3. Thanks to @dvic for the report. Fixes #2.

Astro version 0.9.0

This is the changelog for Astro version 0.9.0 released on October 8th, 2021. For older changelogs please consult the release tag on GitHub

Please note that Elixir 1.11 or later is required.

Enhancements

  • Adds Astro.lunar_phase_emoji/1 to produce a single grapheme string representing the image of the moon phase for a given lunar angle.

Astro version 0.8.0

This is the changelog for Astro version 0.8.0 released on October 3rd, 2021. For older changelogs please consult the release tag on GitHub

Please note that Elixir 1.11 or later is required.

Enhancements

  • Convert some identity functions to macros which improves runtime performance

  • Add additional specs and docs to Astro.Math module

Astro version 0.7.0

This is the changelog for Astro version 0.7.0 released on September 10th, 2021. For older changelogs please consult the release tag on GitHub

Please note that Elixir 1.11 or later is required.

Bug Fixes

  • Revert Astro back to a pure library application. The supervisor for TzWorld still needs to be started. This fix brings the code back into line with the README. Thanks to @dvic for the report. Closes #1.

Astro version 0.6.0

This is the changelog for Astro version 0.6.0 released on September 5th, 2021. For older changelogs please consult the release tag on GitHub

Please note that Elixir 1.11 or later is required.

Bug Fixes

  • Fix Astro.Math.atan_r/2

  • Fix ephemeris calculation

Breaking changes

  • Change Time.date_time_{from, to}_iso_days/1 to Time.date_time_{from, to}_moment/1

Enhancements

Astro version 0.5.0

This is the changelog for Astro version 0.5.0 released on August 26th, 2021. For older changelogs please consult the release tag on GitHub

Please note that Elixir 1.11 or later is required.

Bug Fixes

  • Updates documentation to be clear about installation and setup requirements for tz_world

  • Fixes test data for São Paulo now that it no longer uses DST

  • Ensure :astro is started in test mode

Enhancements

This primary focus of this release is to add lunar calculations for moon phase.

Astro version 0.4.0

This is the changelog for Astro version 0.4.0 released on February 16th, 2020. For older changelogs please consult the release tag on GitHub

Breaking Change

  • When no timezone is found the return is changed from {:error, :timezone_not_found} to {:error, :time_zone_not_found} to be consistent with Elixir and TzData.

Astro version 0.3.0

This is the changelog for Astro version 0.3.0 released on December 9th, 2019. For older changelogs please consult the release tag on GitHub

Change in behaviour

  • Seconds are no longer truncated to zero when calculating datetimes and durations

Enhancements

  • Add Astro.solar_noon/2 to return the true solar noon for a location and date

  • Add Astro.hours_of_daylight/2 to return hours, minutes and seconds as a Time.t() representing the number of daylight hours for a give location and date

  • Add Astro.sun_apparent_longitude/1 to return the apparent solar longitude on a given date. The result, a number of degrees between 0 and 360, can be used to determine the seasons.

Astro version 0.2.0

This is the changelog for Astro version 0.2.0 released on December 6th, 2019. For older changelogs please consult the release tag on GitHub

Enhancements

  • Add Astro.equinox/2and Astro.solstice/2 to calculate solstices and equinoxes for a year. From these can be derived the seasons.

  • Add Astro.Time.datetime_from_julian_days/1

  • Add Astro.Time.utc_datetime_from_terrestrial_datetime/1

Astro version 0.1.0

This is the changelog for Astro version 0.1.0 released on December 5th, 2019. For older changelogs please consult the release tag on GitHub

Enhancements