# Changelog

## Astro version 2.9.0

This is the changelog for Astro version 2.9.0, released on October 26th, 2026. For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Added

* An application can supervise Astro itself: with the dependency marked `runtime: false`, so the `:astro` application is not started, listing `Astro.Supervisor` in the application's own tree loads the JPL ephemeris before the supervisor starts, where only the `:astro` application loaded it. Where the `:astro` application runs as well, the ephemeris it loaded is kept, so an application that lists `Astro.Supervisor` for tz_world's backend is unaffected. `Astro.Supervisor` describes the setup, and the `astro: :load` a release then needs.

### Changed

* JPL positions and the functions built on them are faster, with results unchanged to the last bit:

  * `Astro.Ephemeris.check_coverage/1,2` looks up the ephemeris segments a moment needs, where it computed the Sun's and the Moon's apparent positions (47 µs to 4 µs for a span). Every function that checks coverage first gains: `Astro.solar_noon/2` 92 µs to 49 µs, `Astro.lunar_phase_at/1` 109 µs to 53 µs, `Astro.sun_position_at/1` 74 µs to 26 µs.

  * An ecliptic position of the Sun or the Moon computes the nutation once, where it computed it twice (`Astro.Solar.solar_ecliptic_longitude/1` 19 µs to 14 µs).

  * Sunrise, sunset, moonrise and moonset sample their search window only until the event is bracketed, where they sampled all of it (`Astro.new_visible_crescent/3` 6.0 ms to 4.1 ms).

## Astro version 2.8.0

This is the changelog for Astro version 2.8.0, released on October 23rd, 2026. For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Added

* `Astro.Ephemeris.sun_ecliptic_position/1`, `moon_ecliptic_position/1` and their `_dt` forms return apparent ecliptic longitude, latitude and distance.

* `Astro.Ephemeris.sun_position_from_moment/1` and `moon_position_from_moment/1` return apparent right ascension, declination and distance for a moment.

* `Astro.Coordinates.true_equator_to_ecliptic/2`, `Astro.Coordinates.cartesian_to_ecliptic_spherical/1` and `Astro.Time.moment_from_julian_centuries/1`.

* `Astro.Ephemeris.check_coverage/2` reports whether the loaded ephemeris covers a moment or span of moments.

### Breaking Changes

* `Astro.lunar_phase_at/1`, `illuminated_fraction_of_moon_at/1`, `date_time_new_moon_nearest/1`, `date_time_lunar_phase_at_or_before/2`, `date_time_lunar_phase_at_or_after/2`, `sun_position_at/1`, `moon_position_at/1`, `sun_apparent_longitude/1`, `sun_azimuth_elevation/2` and `solar_noon/2` return `{:error, :not_found}` for dates the loaded ephemeris does not cover (1900–2100 for the bundled file), where 2.7.0 returned a value from the Meeus series.

### Changed

* Solar and lunar positions, ecliptic longitudes, latitudes and distances in `Astro.Solar`, `Astro.Lunar` and `Astro.Lunar.CrescentVisibility` are computed from the JPL DE440s ephemeris instead of the Meeus series. Results shift by seconds of arc; event times by seconds.

* `Astro.Solar.solar_ecliptic_longitude/1`, and so `solar_ecliptic_longitude_after/2` and `estimate_prior_solar_ecliptic_longitude/2`, fall back to the Meeus series for a moment the loaded ephemeris does not cover, where 2.8.0 raised `MatchError`. Lunisolar calendars find their solar terms for any era again.

### Deprecated

* `Astro.Solar.sun_apparent_longitude/1`, `sun_true_longitude/1` and `solar_declination/1` now use the JPL ephemeris; use `solar_ecliptic_longitude/1` and `solar_position/1`, which take a moment.

* `Astro.Solar.obliquity_correction/1` and `mean_obliquity_of_ecliptic/1` now use the IAU 1980 nutation; use `Astro.Earth.nutation/1`.

* `Astro.Solar.sun_equation_of_center/1`, `sun_geometric_mean_anomaly/1`, `earth_orbit_eccentricity/1`, and `Astro.Lunar.mean_lunar_ecliptic_longitude/1` and `lunar_elongation/1` are unchanged and will be removed in Astro 3.0.

### Bug Fixes

* JPL nutation was rotated in the wrong sense, misplacing the Sun and Moon by up to ~30″ and shifting rise and set times by a few seconds. JPL-based equinox instants now match published values to within ~5 seconds.

* The geocentric Sun added the Earth's offset from the Earth–Moon barycentre instead of subtracting it, an error of up to ~9,000 km in solar distance.

* JPL positions are corrected for light time and aberration, so they are apparent rather than geometric positions, as documented.

## Astro version 2.7.0

This is the changelog for Astro version 2.7.0, released on September 25th, 2026. For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Enhancements

* `Astro.Lunar.date_time_new_moon_before/1` and `date_time_new_moon_at_or_after/1` evaluate only the two lunations either side of the moment, about five times faster. Results are unchanged, bit for bit.

* `Astro.Time.dynamical_from_universal/1` and `universal_from_dynamical/1` find the ΔT decimal year with integer day arithmetic, about 1.6 times faster. Results are unchanged on every day of years −9999 to 9999.

* `Astro.equinox/3` and `Astro.solstice/3` take `:time_zone` (`:utc` by default, or a zone name) and `:time_zone_database` options and return the instant in that zone, whose civil date can differ from the UTC date — for Japan's equinox holidays, in about a third of years. A named zone with no time zone database configured returns `{:error, :utc_only_time_zone_database}`.

* `Astro.Supervisor.child_spec/1` lets `Astro.Supervisor`, which starts the tz_world backend, be listed as a child in an application's supervision tree.

### Bug Fixes

* The specs of `Astro.date_time_new_moon_before/1`, `date_time_new_moon_nearest/1`, `date_time_new_moon_at_or_after/1`, `date_time_lunar_phase_at_or_before/2` and `date_time_lunar_phase_at_or_after/2` were malformed, so their error return was silently dropped and dialyzer took them never to fail. With the fix below they cannot fail, so they declare `{:ok, DateTime.t()}` and their docs no longer describe an error shape they never returned.

* `Astro.Time.date_time_from_moment/1`, and so every date-time search above, converts instants before 0000-01-01 instead of returning `{:error, :invalid_time}` — the day of a negative moment was truncated rather than floored.

* The date-time clause of `Astro.date_time_new_moon_before/1` was defined as `Astro.date_time_new_moon_at_or_before/1`, which carried its documentation. It is now a clause of `date_time_new_moon_before/1`, and `date_time_new_moon_at_or_before/1` is deprecated.

* `Astro.lunar_phase_emoji/1` returns the new moon 🌑 for phases above 337.5°, where it returned the crescent moon 🌙, which is not a phase symbol.

* `Astro.Time.hours_and_date_to_date_time/2` declares the `{:error, reason}` it returns for an invalid date or a time of day of 24 hours or more.

* `Astro.Time.date_time_from_date_and_minutes/2` returns `{:error, :invalid_date}` for a date that is not valid in its calendar, where it raised `MatchError`, and converts a date in another calendar to its ISO date instead of reading its fields as ISO. `Astro.solar_noon/2` returns the same errors and gives a date in another calendar the solar noon of that same day.

* `Astro.sun_azimuth_elevation/2`, `Astro.Time.local_sidereal_time/2` and `Astro.Time.greenwich_mean_sidereal_time/1` raised `ArgumentError` for every input in an application with no time zone database configured. They now need none.

* `Astro.sunrise/3` and `Astro.sunset/3` return `{:error, :invalid_solar_elevation}` for an unknown `:solar_elevation`, where they raised `CaseClauseError`, and their docs now list every error they return.

* `Astro.moonrise/3` and `Astro.moonset/3` return `{:error, :invalid_limb}` or `{:error, :invalid_interpolation}` for an unknown `:limb` or `:interpolation`, where they raised `CaseClauseError`. Their docs and specs promised `:moon_always_below_horizon` and `:moon_always_above_horizon` where they return `{:error, :no_time}`, and now list every error they return.

* `Astro.new_visible_crescent/3` with the `:odeh` method, the default, or the `:yallop` method misclassified many crescents — a crescent 36 hours old at Mecca could be "not visible with optical aid" — because the lunar altitude and semi-diameter it uses were wrong (below). Classifications change on about half of evenings with `:odeh` and a quarter with `:yallop`, and the two methods now agree on 79% of evenings, where they agreed on 39%.

* `Astro.Lunar.lunar_altitude/2`, `angular_semi_diameter/1`, `equatorial_horizontal_parallax/1`, `horizontal_dip/1`, `topocentric_lunar_parallax/2` and `topocentric_lunar_altitude/2` returned wrong values, because the arcsine they share treated its ratio argument as degrees. `lunar_altitude/2` now agrees with the JPL ephemeris to within 0.006°.

* `Astro.Time.mean_sidereal_from_moment/1`, and through it `Astro.sun_azimuth_elevation/2`, `Astro.Time.greenwich_mean_sidereal_time/1`, `local_sidereal_time/2` and `Astro.Lunar.lunar_altitude/2`, measured sidereal time from Terrestrial rather than Universal Time, about 0.27° ahead. They now match Meeus's worked examples, and the sun's elevation agrees with the JPL ephemeris to within 0.01°.

* `Astro.Time.apparent_sidereal_from_moment/1` applied the formula for 0h UT at every time of day. It now returns the apparent sidereal time, as `Astro.Coordinates.gast/1` does.

* `Astro.new_visible_crescent/3` with the `:schaefer` method modelled the sky as dark while the Sun was less than 1° below the horizon, so it could report a crescent under an hour old as visible to the naked eye. Twilight now brightens the sky from the horizon down.

* `Astro.Lunar.lunar_node/1` returned the node's distance from the equinoctial point about 9,000 years after the given moment. The doc of `Astro.Lunar.moon_node/1` now says it returns the Moon's argument of latitude, which it always has.

## Astro version 2.6.1

This is the changelog for Astro version 2.6.1, released on September 24th, 2026. For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Enhancements

* The periodic-term series behind lunar phases, new moons, `Astro.moon_position_at/1` and crescent visibility are zipped into tuples at compile time and summed in a single pass, roughly halving their cost. Results are unchanged, bit for bit.

* Sunrise, sunset, moonrise, moonset and crescent visibility are 1.6 to 1.75 times faster: the ephemeris is decoded in one pass per axis and evaluated without per-coefficient closures or list reversals, and its segments are indexed when it loads. Results are unchanged, bit for bit.

* Rise and set functions resolve the location's time zone once per call rather than once per candidate event, which had doubled the lookup for many locations, and `Astro.hours_of_daylight/2` and `Astro.duration_of_daylight/2` reuse sunrise's zone for sunset. A time zone lookup can cost more than the astronomy itself, so calls using the default `:time_zone` gain the most.

## Astro version 2.6.0

This is the changelog for Astro version 2.6.0, released on September 22nd, 2026. For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Breaking Changes

* The minimum supported Elixir version is now 1.17, raised from 1.11. `Astro.duration_of_daylight/2` is therefore always defined, rather than only on releases where `Duration` is available.

### Enhancements

* Supports `tz_world: "~> 2.4"` only to allow use of the `TzWorld.Backend.SpatialIndex` backend.

* Added guides for getting started, solar events and lunar events. Their examples are doctested, so they cannot drift from the library.

### Bug Fixes

* `Astro.hours_of_daylight/2` and `Astro.duration_of_daylight/2` now return the same result on every Elixir release. They derived the day length from `DateTime.diff/2` at second precision, whose treatment of the microsecond components changed in Elixir 1.19, so one location and date returned 14:18:45 on Elixir 1.18 and earlier but 14:18:44 from 1.19 onwards.

* Time zone resolution returns `{:error, :tz_world_data_not_installed}` when `tz_world` is a dependency but its time zone data has never been downloaded, instead of leaking the bare POSIX `{:error, :enoent}`. Running `mix tz_world.update` installs the data.

## Astro version 2.5.0

This is the changelog for Astro version 2.5.0, released on August 9th, 2026. For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Enhancements

* A compact ephemeris covering 1900 to 2100 now ships with the package, so Astro works immediately after installation with no download step. It is extracted from JPL's DE440s kernel and yields identical results; `mix astro.download_ephemeris` remains available for the full 1849 to 2150 range and takes precedence when present.

* `mix astro.build_ephemeris` builds a compact ephemeris from a JPL DE-series kernel, keeping only the Sun, Moon and Earth segments over a chosen span of years at roughly 42 KB per year. Options include `--from`, `--to`, `--source` and `--keep-earth`.

### Bug Fixes

* Ephemeris downloads now pin TLS 1.2. Erlang offers TLS 1.3 by default on OTP 26 and later, but NASA NAIF's server fails that handshake, which surfaced as `{:failed_connect, ..., :closed}` while `curl` appeared to work; this fix was described in the 2.2.2 release notes but the code change was not included until now. Thanks to @allenwyma for the report. Closes #10.

## Astro version 2.4.0

This is the changelog for Astro version 2.4.0 released on July 15th, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Enhancements

* Prefer `Tz.TimeZoneDatabase` over `Tzdata.TimeZoneDatabase` in the compile-time default when both libraries are loaded, remove the `tzdata` dependency entirely, and use `tz` for astro's own development and test environments. Astro remains time zone database agnostic: the `:elixir` `:time_zone_database` runtime configuration takes precedence, any `Calendar.TimeZoneDatabase` implementation works, and neither database is forced on consumers.

## Astro version 2.3.3

This is the changelog for Astro version 2.3.3 released on July 5th, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Bug Fixes

* `Astro.moonrise/3` and `Astro.moonset/3` now return `{:error, :not_found}` for a date outside the ephemeris range instead of raising a `MatchError`, completing the treatment applied to the sun events in 2.3.2. The moon-event scan confirms its search span — padded by one Lagrange interpolation interval — is covered by the ephemeris before computing altitudes.

* `Astro.equinox/2` and `Astro.solstice/2` now return `{:error, :year_out_of_range}` for years outside 1000 CE to 3000 CE (the documented accuracy domain) instead of raising a `FunctionClauseError`. A far-past or far-future date reached through an astronomical calendar such as Persian now fails cleanly.

* `Astro.new_visible_crescent/3,4` now return `{:error, :not_found}` when the date is outside the ephemeris range, distinct from `{:error, :no_sunset}` which is reserved for a genuine polar no-sunset day. Callers can now tell missing data apart from a real astronomical condition.

## Astro version 2.3.2

This is the changelog for Astro version 2.3.2 released on July 4th, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Bug Fixes

* `Astro.sunrise/3` and `Astro.sunset/3` now return `{:error, :not_found}` for a date outside the ephemeris range instead of raising a `MatchError`. The sun-event scan confirms its search window is covered by the ephemeris before computing altitudes, so a far-future or far-past date — such as one reached through an astronomical calendar like Persian — fails cleanly.

## Astro version 2.3.1

This is the changelog for Astro version 2.3.1 released on June 30th, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Bug Fixes

* Fix compilation failure in downstream libraries (such as Calendrical) that compute ancient dates while a non-UTC time zone database like `Tzdata.TimeZoneDatabase` is configured. `Astro.Time.date_time_from_date_and_minutes/2` performed UTC-only arithmetic via the configured time zone database, which can return `:time_zone_not_found` for dates outside its range; it now uses `Calendar.UTCOnlyTimeZoneDatabase` for that arithmetic. Thanks to @probably-not for the report.

## Astro version 2.3.0

This is the changelog for Astro version 2.3.0 released on June 19th, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Enhancements

* Add `duration_of_daylight/2`, returning the duration of daylight for a location and date as a `t:Duration.t/0`. Unlike `hours_of_daylight/2` (which returns a `t:Time.t/0` capped at `~T[23:59:59]`), it represents a full 24 hours of daylight in the polar summer as `%Duration{hour: 24}`. It is defined only on Elixir 1.17 and later, where the `Duration` module is available.

## Astro version 2.2.3

This is the changelog for Astro version 2.2.3 released on June 15th, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Bug Fixes

* Fix hours_of_daylight/2 for sub-polar latitudes near the solstice. Thanks to @andykent for the issue. Closes #11.

## Astro version 2.2.2

This is the changelog for Astro version 2.2.2 released on June 9th, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Addendum

* The fix for #10 did not land in this release. It landed in 2.5.0 on August 9th, 2026.

### Bug Fixes

* Fix ephemeris download failing with `:failed_connect`/`:closed` on OTP 26+, where Erlang offers TLS 1.3 by default but NASA NAIF's server has a broken TLS 1.3 handshake. Both `mix astro.download_ephemeris` and the runtime auto-downloader now pin to TLS 1.2 (the version `curl` already negotiates). Thanks to @allenwyma for the report. Closes #10.

## Astro version 2.2.1

This is the changelog for Astro version 2.2.1 released on May 23rd, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Bug Fixes

* Fix date_time_from_julian_days to always return proleptic-Gregorian dates.

## Astro version 2.2.0

This is the changelog for Astro version 2.2.0 released on May 21st, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Bug Fixes

* Recover from unwriteable ephemeric download directory by attempting to write to `/temp/astro`

### Enhancements

* Improve logging for the ephemeric downloading events to aid debugging.

## Astro version 2.1.1

This is the changelog for Astro version 2.1.1 released on April 25th, 2026.  For older changelogs please consult the release tag on [GitHub](https://github.com/kipcole9/astro/tags)

### Bug Fixes

* Properly ensure `tz_world` is actually optional.

## 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.