@spec date_time_lunar_phase_at_or_after(date(), phase()) :: {:ok, Calendar.datetime()}

Returns the date time of a given lunar phase at or after a given date time or date.

Arguments

• date_time is a DateTime.t/0 or a Date.t/0 or any struct that meets the requirements of Calendar.date/0 or Calendar.datetime/0.

• phase is the required lunar phase expressed as a float number of degrees between 0.0 and 360.0.

Returns

• {:ok, date_time} at which the phase occurs or

• {:error, {module, reason}}

Example

iex> Astro.date_time_lunar_phase_at_or_after(~D[2021-08-01], Astro.Lunar.full_moon_phase())
{:ok, ~U[2021-08-22 12:02:02.816534Z]}

@spec date_time_lunar_phase_at_or_before(date(), phase()) ::
  {:ok, Calendar.datetime()}

Returns the date time of a given lunar phase at or before a given date time or date.

Arguments

• date_time is a DateTime.t/0 or a Date.t/0 or any struct that meets the requirements of Calendar.date/0 or Calendar.datetime/0.

• phase is the required lunar phase expressed as a float number of degrees between 0.0 and 3660.0.

Returns

• {:ok, date_time} at which the phase occurs or

• {:error, {module, reason}}

Example

iex> Astro.date_time_lunar_phase_at_or_before(~D[2021-08-01], Astro.Lunar.new_moon_phase())
{:ok, ~U[2021-07-10 01:16:34.022607Z]}

@spec date_time_new_moon_at_or_after(date()) :: {:ok, Calendar.datetime()}

Returns the date time of the new moon at or after a given date or date time.

Arguments

• date_time is a DateTime or a Date or any struct that meets the requirements of t:Calendar.date or t:Calendar.datetime.

Returns

• {:ok, date_time} at which the new moon occurs or

• {:error, {module, reason}}

Example

iex> Astro.date_time_new_moon_at_or_after(~D[2021-08-23])
{:ok, ~U[2021-09-07 00:51:44.267320Z]}

Returns the date time of the new moon before a given date or date time.

Arguments

• date_time is a DateTime.t/0 or a Date.t/0 or any struct that meets the requirements of Calendar.date/0 or Calendar.datetime/0.

Returns

• {:ok, date_time} at which the new moon occurs or

• {:error, {module, reason}}

Example

iex> Astro.date_time_new_moon_before(~D[2021-08-23])
{:ok, ~U[2021-08-08 13:50:07.634598Z]}

@spec date_time_new_moon_nearest(date()) :: {:ok, Calendar.datetime()}

Returns the date time of the new moon nearest to a given date or date time.

Arguments

• date_time is a DateTime.t/0 or a Date.t/0 or any struct that meets the requirements of Calendar.date/0 or Calendar.datetime/0.

Returns

• {:ok, date_time} at which the new moon occurs or

• {:error, {module, reason}}

Example

iex> Astro.date_time_new_moon_nearest(~D[2021-08-23])
{:ok, ~U[2021-08-08 13:50:07.490242Z]}

@spec equinox(Calendar.year(), :march | :september) :: {:ok, DateTime.t()}

Returns the datetime in UTC for either the March or September equinox.

Arguments

• year is the gregorian year for which the equinox is to be calculated.

• event is either :march or :september indicating which of the two annual equinox datetimes is required.

Returns

• {:ok, datetime} representing the UTC datetime of the equinox.

Examples

iex> {:ok, dt} = Astro.equinox 2019, :march
iex> DateTime.truncate(dt, :second)
~U[2019-03-20 21:58:28Z]
iex> {:ok, dt} = Astro.equinox 2019, :september
iex> DateTime.truncate(dt, :second)
~U[2019-09-23 07:49:52Z]

Notes

This equinox calculation is expected to be accurate to within 2 minutes for the years 1000 CE to 3000 CE.

An equinox is commonly regarded as the instant of time when the plane of earth's equator passes through the center of the Sun. This occurs twice each year: around 20 March and 23 September.

In other words, it is the moment at which the center of the visible sun is directly above the equator.

@spec hours_of_daylight(location(), Calendar.date()) :: {:ok, Time.t()}

Returns the number of hours of daylight for a given location on a given date.

Arguments

• location is the latitude, longitude and optionally elevation for the desired hours of daylight. It can be expressed as:

  • {lng, lat} - a tuple with longitude and latitude as floating point numbers. Note the order of the arguments.
  • a Geo.Point.t struct to represent a location without elevation
  • a Geo.PointZ.t struct to represent a location and elevation.

• date is any Date.t/0 in the Gregorian calendar (for example, Calendar.ISO).

Returns

• {:ok, time} where time is a Time.t()

Examples

iex> Astro.hours_of_daylight {151.20666584, -33.8559799094}, ~D[2019-12-08]
{:ok, ~T[14:19:29]}

# No sunset in summer
iex> Astro.hours_of_daylight {-62.3481, 82.5018}, ~D[2019-06-07]
{:ok, ~T[23:59:59]}

# No sunrise in winter
iex> Astro.hours_of_daylight {-62.3481, 82.5018}, ~D[2019-12-07]
{:ok, ~T[00:00:00]}

Notes

In latitudes above the polar circles (approximately +/- 66.5631 degrees) there will be no hours of daylight in winter and 24 hours of daylight in summer.

@spec illuminated_fraction_of_moon_at(date()) :: number()

Returns the illumination of the moon as a float for a given date or date time.

Arguments

• date_time is a DateTime.t/0 or a Date.t/0 or any struct that meets the requirements of Calendar.date/0 or Calendar.datetime/0.

Returns

• a float value between 0.0 and 1.0 representing the fractional illumination of the moon.

Example

iex> fraction = Astro.illuminated_fraction_of_moon_at(~D[2017-03-16])
iex> Float.round(fraction, 4)
0.8884

iex> fraction = Astro.illuminated_fraction_of_moon_at(~D[1992-04-12])
iex> Float.round(fraction, 4)
0.6786

@spec lunar_phase_at(date()) :: phase()

Returns the lunar phase as a float number of degrees at a given date or date time.

Arguments

• date_time is a DateTime.t/0 or a Date.t/0 or any struct that meets the requirements of Calendar.date/0 or Calendar.datetime/0.

Returns

• the lunar phase as a float number of degrees.

Example

iex> Astro.lunar_phase_at ~U[2021-08-22 12:02:02.816534Z]
180.00004404669988

iex> Astro.lunar_phase_at(~U[2021-07-10 01:16:34.022607Z])
3.6600909621461326e-6

@spec lunar_phase_emoji(phase()) :: String.t()

Returns the moon phase as a UTF8 binary representing an emoji of the moon phase.

Arguments

• phase is a moon phase between 0.0 and 360.0.

Returns

• A single grapheme string representing the Unicode moon phase emoji.

Examples

iex> Astro.lunar_phase_emoji 0
"🌑"
iex> Astro.lunar_phase_emoji 45
"🌒"
iex> Astro.lunar_phase_emoji 90
"🌓"
iex> Astro.lunar_phase_emoji 135
"🌔"
iex> Astro.lunar_phase_emoji 180
"🌕"
iex> Astro.lunar_phase_emoji 245
"🌖"
iex> Astro.lunar_phase_emoji 270
"🌗"
iex> Astro.lunar_phase_emoji 320
"🌘"
iex> Astro.lunar_phase_emoji 360
"🌑"

iex> ~U[2021-08-22 12:02:02.816534Z]
...> |> Astro.lunar_phase_at()
...> |> Astro.lunar_phase_emoji()
"🌕"

@spec moon_position_at(date()) :: Geo.PointZ.t()

Returns a t:Geo.PointZ containing the right ascension and declination of the moon at a given date or date time.

Arguments

• date_time is a DateTime.t/0 or a Date.t/0 or any struct that meets the requirements of Calendar.date/0 or Calendar.datetime/0.

Returns

• a t:Geo.PointZ struct with coordinates {right_ascension, declination, distance} with properties %{reference: :celestial, object: :moon} distance is in meters.

Example

iex> Astro.moon_position_at(~D[1992-04-12]) |> Astro.Location.round(6)
%Geo.PointZ{
  coordinates: {134.69343, 13.766512, 368409007.322444},
  properties: %{object: :moon, reference: :celestial},
  srid: nil
}

@spec moonrise(location(), date(), options()) ::
  {:ok, DateTime.t()} | {:error, :moon_always_below_horizon}

Returns the datetime of moonrise for a given location and date.

Uses the JPL DE440s ephemeris with fully topocentric correction to compute the Moon's altitude zero-crossing via scan-and-bisect.

Arguments

• location is the location as a {longitude, latitude} tuple, a Geo.Point.t or a Geo.PointZ.t.

• date is a Date.t/0 or DateTime.t/0.

• options is a keyword list of options.

Options

• :time_zone is the time zone in which the sunrise is requested. The default is :default in which the sunrise time is reported in the time zone of the requested location. :utc can be specified or any other time zone name supported by the option :time_zone_database is acceptabe.

• :time_zone_database represents the module that implements the Calendar.TimeZoneDatabase behaviour. The default is the configured Elixir time zone database or one of Tzdata.TimeZoneDatabase or Tz.TimeZoneDatabase depending upon which dependency is configured.

• :time_zone_resolver is a 1-arity function that resolves the time zone name for a given location. The function will receive a %Geo.Point{cordinates: {lng, lat}} struct and is expected to return either {:ok, time_zone_name} or {:error, :time_zone_not_found}. The default is TzWorld.timezone_at/1 if :tz_world is configured.

Returns

• {:ok, date_time} with the local time of moonrise, or

• {:error, :moon_always_below_horizon} if the Moon does not rise on the given date at the given location.

@spec moonset(location(), date(), options()) ::
  {:ok, DateTime.t()} | {:error, :moon_always_above_horizon}

Returns the datetime of moonset for a given location and date.

Uses the JPL DE440s ephemeris with fully topocentric correction to compute the Moon's altitude zero-crossing via scan-and-bisect.

Arguments

• location is the location as a {longitude, latitude} tuple, a Geo.Point.t or a Geo.PointZ.t.

• date is a Date.t/0 or DateTime.t/0.

• options is a keyword list of options.

Options

• :time_zone is the time zone in which the sunrise is requested. The default is :default in which the sunrise time is reported in the time zone of the requested location. :utc can be specified or any other time zone name supported by the option :time_zone_database is acceptabe.

• :time_zone_database represents the module that implements the Calendar.TimeZoneDatabase behaviour. The default is the configured Elixir time zone database or one of Tzdata.TimeZoneDatabase or Tz.TimeZoneDatabase depending upon which dependency is configured.

• :time_zone_resolver is a 1-arity function that resolves the time zone name for a given location. The function will receive a %Geo.Point{cordinates: {lng, lat}} struct and is expected to return either {:ok, time_zone_name} or {:error, :time_zone_not_found}. The default is TzWorld.timezone_at/1 if :tz_world is configured.

Returns

• {:ok, date_time} with the local time of moonset, or

• {:error, :moon_always_above_horizon} if the Moon does not set on the given date at the given location.

@spec new_visible_crescent(location(), date(), method()) ::
  {:ok, Astro.Lunar.CrescentVisibility.visibility()} | {:error, :no_sunset}

Predicts the visibility of the new crescent moon at a given location on a given date using one of three published criteria.

At the optimal observation time after sunset, the function evaluates the geometric and photometric conditions to classify the crescent into one of five visibility categories.

Arguments

• location is the latitude, longitude and optionally elevation for the observation site. It can be expressed as:

  • {lng, lat} - a tuple with longitude and latitude as floating point numbers. Note the order of the arguments.

  • a Geo.Point.t/0 struct to represent a location without elevation.

  • a Geo.PointZ.t/0 struct to represent a location and elevation.

• date is a Date.t/0 or DateTime.t/0 indicating the evening on which crescent visibility is to be evaluated.

• method selects the prediction criterion. Default :odeh.

  • :odeh — Odeh (2006). Empirical criterion based on 737 observations. Uses topocentric ARCV with a Danjon limit of 6.4°. The most widely used modern criterion.

  • :yallop — Yallop (1997). Empirical criterion based on 295 observations. Uses geocentric ARCV. The original single-parameter approach that Odeh later refined.

  • :schaefer — Schaefer (1988/2000). Physics-based model computing the contrast between crescent brightness and twilight sky brightness against the human contrast detection threshold. The best observation time is found by scanning from sunset to moonset.

Options

When method is :schaefer, the following options are accepted as an optional fourth argument (a keyword list):

• :extinction — V-band zenith extinction coefficient. Default 0.172 (clean sea-level site). Typical values: 0.12 (high mountain), 0.17 (sea level), 0.25 (hazy conditions).

Returns

• {:ok, visibility} where visibility is one of:

  • :A — Visible to the naked eye.

  • :B — Visible with optical aid.

  • :C — May need optical aid.

  • :D — Not visible with optical aid.

  • :E — Not visible.

• {:error, :no_sunset} if no sunset occurs on the given date at the given location (e.g. polar day).

Method comparison

Examples

iex> location = {-0.1275, 51.5072}
iex> Astro.new_visible_crescent(location, ~D[2025-03-31])
{:ok, :A}

iex> location = {-0.1275, 51.5072}
iex> Astro.new_visible_crescent(location, ~D[2025-03-31], :yallop)
{:ok, :A}

@spec new_visible_crescent(location(), date(), :schaefer, keyword()) ::
  {:ok, Astro.Lunar.CrescentVisibility.visibility()} | {:error, :no_sunset}

Same as new_visible_crescent/3 with method: :schaefer but accepts additional atmospheric options.

See new_visible_crescent/3 for full documentation.

Options

• :extinction — V-band zenith extinction coefficient. Default 0.172.

Example

iex> location = {39.8579, 21.3891}
iex> {:ok, visibility} = Astro.new_visible_crescent(location, ~D[2025-03-31], :schaefer, extinction: 0.25)
iex> visibility in [:A, :B, :C, :D, :E]
true

@spec solar_noon(location(), Calendar.date()) :: {:ok, DateTime.t()}

Returns solar noon for a given date and location as a UTC datetime

Arguments

• location is the latitude, longitude and optionally elevation for the desired solar noon time. It can be expressed as:

  • {lng, lat} - a tuple with longitude and latitude as floating point numbers. Note the order of the arguments.
  • a Geo.Point.t struct to represent a location without elevation.
  • a Geo.PointZ.t struct to represent a location and elevation.

• date is any Date.t/0 in the Gregorian calendar (for example, Calendar.ISO).

Returns

• a UTC datetime representing solar noon at the given location for the given date.

Example

iex> Astro.solar_noon {151.20666584, -33.8559799094}, ~D[2019-12-06]
{:ok, ~U[2019-12-06 01:45:42Z]}

Notes

Solar noon is the moment when the sun passes a location's meridian and reaches its highest position in the sky. In most cases, it doesn't happen at 12 o'clock.

At solar noon, the Sun reaches its highest position in the sky as it passes the local meridian.

@spec solstice(Calendar.year(), :june | :december) :: {:ok, DateTime.t()}

Returns the datetime in UTC for either the June or December solstice.

Arguments

• year is the gregorian year for which the solstice is to be calculated.

• event is either :june or :december indicating which of the two annual solstice datetimes is required.

Returns

• {:ok, datetime} representing the UTC datetime of the solstice.

Examples

iex> {:ok, dt} = Astro.solstice 2019, :december
iex> DateTime.truncate(dt, :second)
~U[2019-12-22 04:19:19Z]
iex> {:ok, dt} = Astro.solstice 2019, :june
iex> DateTime.truncate(dt, :second)
~U[2019-06-21 15:54:07Z]

Notes

This solstice calculation is expected to be accurate to within 2 minutes for the years 1000 CE to 3000 CE.

A solstice is an event occurring when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21.

The seasons of the year are determined by reference to both the solstices and the equinoxes.

The day of a solstice in either hemisphere has either the most sunlight of the year (summer solstice) or the least sunlight of the year (winter solstice) for any place other than the Equator.

Alternative terms, with no ambiguity as to which hemisphere is the context, are "June solstice" and "December solstice", referring to the months in which they take place every year.

@spec sun_apparent_longitude(Calendar.date()) :: degrees()

Returns solar longitude for a given date. Solar longitude is used to identify the seasons.

Arguments

• date is any Date.t/0 in the Gregorian calendar (for example, Calendar.ISO).

Returns

• a float number of degrees between 0 and 360 representing the solar longitude on date.

Examples

iex> Astro.sun_apparent_longitude ~D[2019-03-21]
0.08035853207991295
iex> Astro.sun_apparent_longitude ~D[2019-06-22]
90.32130455695378
iex> Astro.sun_apparent_longitude ~D[2019-09-23]
179.68691978440197
iex> Astro.sun_apparent_longitude ~D[2019-12-23]
270.83941087483504

Notes

Solar longitude (the ecliptic longitude of the sun) in effect describes the position of the earth in its orbit, being zero at the moment of the March equinox.

Since it is based on how far the earth has moved in its orbit since the equinox, it is a measure of what time of the tropical year (the year of seasons) we are in, but without the inaccuracies of a calendar date, which is perturbed by leap years and calendar imperfections.

@spec sun_azimuth_elevation(location(), Calendar.datetime()) ::
  {azimuth :: float(), altitude :: float()}

Returns a tuple {azimuth, altitude} for a given date time and location.

Arguments

• location is the latitude, longitude and optionally elevation for the desired sunrise azimuth and altitude. It can be expressed as:

  • {lng, lat} - a tuple with longitude and latitude as floating point numbers. Note the order of the arguments.
  • a Geo.Point.t struct to represent a location without elevation
  • a Geo.PointZ.t struct to represent a location and elevation

• date_time is a DateTime.t/0 or a Date.t/0 or any struct that meets the requirements of Calendar.date/0 or Calendar.datetime/0.

Returns

• a tuple of the format {azimith, altitude} which are expressed in float degrees.

Example

iex> {:ok, date_time} = DateTime.new(~D[2023-05-17], ~T[12:47:00], "Australia/Sydney")
iex> location = {151.1637781, -33.5145852}
iex> {_azimuth, _altitude} = Astro.sun_azimuth_elevation(location, date_time)

@spec sun_position_at(date()) :: Geo.PointZ.t()

Returns a t:Geo.PointZ containing the right ascension and declination of the sun at a given date or date time.

Arguments

• date_time is a DateTime.t/0 or a t:Date/0 or any struct that meets the requirements of Calendar.date/0 or Calendar.datetime/0.

Returns

• a Geo.PointZ.t/0 struct with coordinates {right_ascension, declination, distance} with properties %{reference: :celestial, object: :sun}. distance is in meters.

Example

iex> Astro.sun_position_at(~D[1992-10-13])
%Geo.PointZ{
  coordinates: {-161.61854343627374, -7.785324796344723, 149169604737.93973},
  properties: %{object: :sun, reference: :celestial},
  srid: nil
}

@spec sunrise(location(), date(), options()) ::
  {:ok, DateTime.t()}
  | {:error, :time_zone_not_found | :time_zone_not_resolved | :no_time}

Calculates the sunrise for a given location and date.

Sunrise is the moment when the upper limb of the sun appears on the horizon in the morning.

Arguments

• location is the latitude, longitude and optionally elevation for the desired sunrise time. It can be expressed as:

  • {lng, lat} - a tuple with longitude and latitude as floating point numbers. Note the order of the arguments.
  • a Geo.Point.t/0 struct to represent a location without elevation
  • a Geo.PointZ.t/0 struct to represent a location and elevation

• date is a Date.t/0, NaiveDateTime.t/0 or DateTime.t/0 to indicate the date of the year in which the sunrise time is required.

• options is a keyword list of options.

Options

• solar_elevation represents the type of sunrise required. The default is :geometric which equates to a solar elevation of 90°. In this case the calculation also accounts for refraction and elevation to return a result which accords with the eye's perception. Other solar elevations are:

  • :civil representing a solar elevation of 96.0°. At this point the sun is just below the horizon so there is generally enough natural light to carry out most outdoor activities.

  • :nautical representing a solar elevation of 102.0° This is the point at which the horizon is just barely visible and the moon and stars can still be used for navigation.

  • :astronomical representing a solar elevation of 108.0°. This is the point beyond which astronomical observation becomes impractical.

  • Any floating point number representing the desired solar elevation.

• :time_zone is the time zone in which the sunrise is requested. The default is :default in which the sunrise time is reported in the time zone of the requested location. :utc can be specified or any other time zone name supported by the option :time_zone_database is acceptabe.

• :time_zone_database represents the module that implements the Calendar.TimeZoneDatabase behaviour. The default is the configured Elixir time zone database or one of Tzdata.TimeZoneDatabase or Tz.TimeZoneDatabase depending upon which dependency is configured.

• :time_zone_resolver is a 1-arity function that resolves the time zone name for a given location. The function will receive a %Geo.Point{cordinates: {lng, lat}} struct and is expected to return either {:ok, time_zone_name} or {:error, :time_zone_not_found}. The default is TzWorld.timezone_at/1 if :tz_world is configured.

Returns

• a DateTime.t/0 representing the time of sunrise in the requested time zone at the requested location.

• {:error, :time_zone_not_found} if the requested time zone is unknown.

• {:error, :time_zone_not_resolved} if it is not possible to resolve a time zone name from the location. This can happen if :tz_world is not configured as a dependency and no :time_zone_resolver option is specified.

• {:error, :no_time} if for the requested date and location there is no sunrise. This can occur at very high and very low latitudes during summer and winter.

Notes

• If the resolved UTC date time is ambiguous because of a daylight savings transition, the second of the two possibilities is applied. See the DateTime.from_naive/3 for more information.

Examples

# Sunrise in Sydney, Australia
Astro.sunrise({151.20666584, -33.8559799094}, ~D[2019-12-04])
{:ok, #DateTime<2019-12-04 05:37:00.000000+11:00 AEDT Australia/Sydney>}

# Sunrise in Alert, Nanavut, Canada
Astro.sunrise({-62.3481, 82.5018}, ~D[2019-12-04])
{:error, :no_time}

@spec sunset(location(), date(), options()) ::
  {:ok, DateTime.t()}
  | {:error, :time_zone_not_found | :time_zone_not_resolved | :no_time}

Calculates the sunset for a given location and date.

Sunset is the moment when the upper limb of the sun disappears below the horizon in the evening.

Arguments

• location is the latitude, longitude and optionally elevation for the desired sunrise time. It can be expressed as:

  • {lng, lat} - a tuple with longitude and latitude as floating point numbers. Note the order of the arguments.
  • a Geo.Point.t struct to represent a location without elevation
  • a Geo.PointZ.t struct to represent a location and elevation

• date is a Date.t/0, NaiveDateTime.t/0 or DateTime.t/0 to indicate the date of the year in which the sunset time is required.

• options is a keyword list of options.

Options

• solar_elevation represents the type of sunset required. The default is :geometric which equates to a solar elevation of 90°. In this case the calulation also accounts for refraction and elevation to return a result which accords with the eyes perception. Other solar elevations are:

  • :civil representing a solar elevation of 96.0°. At this point the sun is just below the horizon so there is generally enough natural light to carry out most outdoor activities.

  • :nautical representing a solar elevation of 102.0° This is the point at which the horizon is just barely visible and the moon and stars can still be used for navigation.

  • :astronomicalrepresenting a solar elevation of 108.0°. This is the point beyond which astronomical observation becomes impractical.

  • Any floating point number representing the desired solar elevation.

• :time_zone is the time zone in which the sunset is requested. The default is :default in which the sunrise time is reported in the time zone of the requested location. :utc can be specified or any other time zone name supported by the option :time_zone_database is acceptabe.

• :time_zone_database represents the module that implements the Calendar.TimeZoneDatabase behaviour. The default is the configured Elixir time zone database or one of Tzdata.TimeZoneDatabase or Tz.TimeZoneDatabase depending upon which dependency is configured.

• :time_zone_resolver is a 1-arity function that resolves the time zone name for a given location. The function will receive a %Geo.Point{cordinates: {lng, lat}} struct and is expected to return either {:ok, time_zone_name} or {:error, :time_zone_not_found}. The default is TzWorld.timezone_at/1 if :tz_world is configured.

Returns

• a DateTime.t/0 representing the time of sunset in the requested time zone at the requested location.

• {:error, :time_zone_not_found} if the requested time zone is unknown.

• {:error, :time_zone_not_resolved} if it is not possible to resolve a time zone name from the location. This can happen if :tz_world is not configured as a dependency and no :time_zone_resolver option is specified.

• {:error, :no_time} if for the requested date and location there is no sunset. This can occur at very high and very low latitudes during summer and winter.

Notes

• If the resolved UTC date time is ambiguous because of a daylight savings transition, the second of the two possibilities is applied. See the DateTime.from_naive/3 for more information.

Examples

# Sunset in Sydney, Australia
Astro.sunset({151.20666584, -33.8559799094}, ~D[2019-12-04])
{:ok, #DateTime<2019-12-04 19:53:00.000000+11:00 AEDT Australia/Sydney>}

# Sunset in Alert, Nanavut, Canada
Astro.sunset({-62.3481, 82.5018}, ~D[2019-12-04])
{:error, :no_time}