# Changelog

## 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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

* Add `Astro.moonrise/3` and `Astro.moonset/3` to compute moonrise and moonset times for a given location and date.

* Add `Astro.date_time_new_moon_nearest/1` which returns the new moon nearest to a given date or datetime.

* Add `Astro.Lunar.date_time_new_moon_nearest/1` (takes a moment parameter).

* Add `Astro.Time.date_from_julian_days/1` to convert Julian Day Numbers to `Date` structs.

* Add new `Astro.Solar.SunRiseSet` module implementing sunrise/sunset via JPL DE440s ephemeris and scan-and-bisect solver with configurable bisection tolerance.

* Add new `Astro.Lunar.MoonRiseSet` module implementing fully topocentric moonrise/moonset via JPL DE440s ephemeris and scan-and-bisect solver with configurable bisection tolerance.

* Add new `Astro.Coordinates` module for coordinate system conversions.

* Add new types `Astro.radians/0`, `Astro.astronomical_units/0`, and `Astro.kilometers/0`.

* Improved documentation with greater explanation of some of the key astronomical concepts.

## 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

**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](https://github.com/kipcole9/astro/tags)

**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](https://github.com/kipcole9/astro/tags)

**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](/readme.html). 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](https://github.com/kipcole9/astro/tags)

**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

* Remove dependency on `ex_cldr_calendar` and `jason`

* Add `Astro.sun_position_at/1`

* Add `Astro.moon_position_at/1`

* Add `Astro.illuminated_fraction_of_moon_at/1`

## 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](https://github.com/kipcole9/astro/tags)

**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.

* Adds `Astro.date_time_new_moon_before/1`

* Adds `Astro.date_time_new_moon_at_or_after/1`

* Adds `Astro.lunar_phase_at/1`

* Adds `Astro.date_time_lunar_phase_at_or_before/2`

* Adds `Astro.date_time_lunar_phase_at_or_after/2`

## 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### 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](https://github.com/kipcole9/astro/tags)

### Enhancements

* Add `Astro.equinox/2`and `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](https://github.com/kipcole9/astro/tags)

### Enhancements

* Initial release includes `Astro.sunrise/3` and `Astro.sunset/3`.  See the readme for further roadmap details.