diff --git a/README.md b/README.md
index abb6611..a45a90c 100644
--- a/README.md
+++ b/README.md
@@ -121,6 +121,36 @@ observation_events.setting_azimuth.str(:dms)
 # => "+250° 23′ 33.6177″"
 ```
 
+### Twilight times
+
+```rb
+epoch = Astronoby::Epoch.from_time(Date.new(2024, 1, 1))
+sun = Astronoby::Sun.new(epoch: epoch)
+observer = Astronoby::Observer.new(
+  latitude: Astronoby::Angle.from_degrees(48.8566),
+  longitude: Astronoby::Angle.from_degrees(2.3522)
+)
+twilight_events = sun.twilight_events(observer: observer)
+
+twilight_events.morning_astronomical_twilight_time
+# => 2024-01-01 05:47:24 UTC
+
+twilight_events.morning_nautical_twilight_time
+# => 2024-01-01 06:25:41 UTC
+
+twilight_events.morning_civil_twilight_time
+# => 2024-01-01 07:05:51 UTC
+
+twilight_events.evening_civil_twilight_time
+# => 2024-01-01 16:37:37 UTC
+
+twilight_events.evening_nautical_twilight_time
+# => 2024-01-01 17:17:46 UTC
+
+twilight_events.evening_astronomical_twilight_time
+# => 2024-01-01 17:56:03 UTC
+```
+
 ### Solstice and Equinox times
 
 ```rb
diff --git a/lib/astronoby.rb b/lib/astronoby.rb
index c5b3342..49eb0df 100644
--- a/lib/astronoby.rb
+++ b/lib/astronoby.rb
@@ -12,6 +12,7 @@
 require "astronoby/equinox_solstice"
 require "astronoby/errors"
 require "astronoby/events/observation_events"
+require "astronoby/events/twilight_events"
 require "astronoby/geocentric_parallax"
 require "astronoby/mean_obliquity"
 require "astronoby/nutation"
diff --git a/lib/astronoby/bodies/sun.rb b/lib/astronoby/bodies/sun.rb
index af7f242..45e534a 100644
--- a/lib/astronoby/bodies/sun.rb
+++ b/lib/astronoby/bodies/sun.rb
@@ -23,6 +23,8 @@ class Sun
       EVENING = :evening
     ].freeze
 
+    attr_reader :epoch
+
     # Source:
     #  Title: Practical Astronomy with your Calculator or Spreadsheet
     #  Authors: Peter Duffett-Smith and Jonathan Zwart
@@ -120,40 +122,10 @@ def observation_events(observer:)
       )
     end
 
-    # @param observer [Astronoby::Observer] Observer of the event
-    # @return [Time, nil] Time the morning civil twilight starts
-    def morning_civil_twilight_time(observer:)
-      twilight_time(CIVIL, MORNING, observer)
-    end
-
-    # @param observer [Astronoby::Observer] Observer of the event
-    # @return [Time, nil] Time the evening civil twilight ends
-    def evening_civil_twilight_time(observer:)
-      twilight_time(CIVIL, EVENING, observer)
-    end
-
-    # @param observer [Astronoby::Observer] Observer of the event
-    # @return [Time, nil] Time the morning nautical twilight starts
-    def morning_nautical_twilight_time(observer:)
-      twilight_time(NAUTICAL, MORNING, observer)
-    end
-
-    # @param observer [Astronoby::Observer] Observer of the event
-    # @return [Time, nil] Time the evening nautical twilight ends
-    def evening_nautical_twilight_time(observer:)
-      twilight_time(NAUTICAL, EVENING, observer)
-    end
-
-    # @param observer [Astronoby::Observer] Observer of the event
-    # @return [Time, nil] Time the morning astronomical twilight starts
-    def morning_astronomical_twilight_time(observer:)
-      twilight_time(ASTRONOMICAL, MORNING, observer)
-    end
-
-    # @param observer [Astronoby::Observer] Observer of the event
-    # @return [Time, nil] Time the evening astronomical twilight ends
-    def evening_astronomical_twilight_time(observer:)
-      twilight_time(ASTRONOMICAL, EVENING, observer)
+    # @param observer [Astronoby::Observer] Observer of the events
+    # @return [Astronoby::Events::TwilightEvents] Sun's twilight events
+    def twilight_events(observer:)
+      Events::TwilightEvents.new(sun: self, observer: observer)
     end
 
     # @return [Numeric] Earth-Sun distance in meters
@@ -232,66 +204,5 @@ def distance_angular_size_factor
 
       term1 / term2
     end
-
-    def current_date
-      Epoch.to_utc(@epoch).to_date
-    end
-
-    # Source:
-    #  Title: Practical Astronomy with your Calculator or Spreadsheet
-    #  Authors: Peter Duffett-Smith and Jonathan Zwart
-    #  Edition: Cambridge University Press
-    #  Chapter: 50 - Twilight
-    def twilight_time(twilight, period_of_the_day, observer)
-      observation_events = observation_events(observer: observer)
-      period_time = if period_of_the_day == MORNING
-        observation_events.rising_time
-      else
-        observation_events.setting_time
-      end
-
-      hour_angle_at_period = equatorial_coordinates_at_midday
-        .compute_hour_angle(time: period_time, longitude: observer.longitude)
-
-      zenith_angle = TWILIGHT_ANGLES[twilight]
-
-      term1 = zenith_angle.cos -
-        observer.latitude.sin *
-          equatorial_coordinates_at_midday.declination.sin
-      term2 = observer.latitude.cos *
-        equatorial_coordinates_at_midday.declination.cos
-      hour_angle_ratio_at_twilight = term1 / term2
-      return nil unless hour_angle_ratio_at_twilight.between?(-1, 1)
-
-      hour_angle_at_twilight = Angle.acos(hour_angle_ratio_at_twilight)
-      time_sign = -1
-
-      if period_of_the_day == MORNING
-        hour_angle_at_twilight =
-          Angle.from_degrees(360 - hour_angle_at_twilight.degrees)
-        time_sign = 1
-      end
-
-      twilight_in_hours =
-        time_sign * (hour_angle_at_twilight - hour_angle_at_period).hours *
-        GreenwichSiderealTime::SIDEREAL_MINUTE_IN_UT_MINUTE
-      twilight_in_seconds = time_sign * twilight_in_hours * 3600
-      (period_time + twilight_in_seconds).round
-    end
-
-    def midday
-      utc_from_epoch = Epoch.to_utc(@epoch)
-      Time.utc(
-        utc_from_epoch.year,
-        utc_from_epoch.month,
-        utc_from_epoch.day,
-        12
-      )
-    end
-
-    def equatorial_coordinates_at_midday
-      apparent_ecliptic_coordinates
-        .to_apparent_equatorial(epoch: Epoch.from_time(midday))
-    end
   end
 end
diff --git a/lib/astronoby/events/twilight_events.rb b/lib/astronoby/events/twilight_events.rb
new file mode 100644
index 0000000..3d0f2da
--- /dev/null
+++ b/lib/astronoby/events/twilight_events.rb
@@ -0,0 +1,114 @@
+# frozen_string_literal: true
+
+module Astronoby
+  module Events
+    class TwilightEvents
+      TWILIGHTS = [
+        CIVIL = :civil,
+        NAUTICAL = :nautical,
+        ASTRONOMICAL = :astronomical
+      ].freeze
+
+      TWILIGHT_ANGLES = {
+        CIVIL => Angle.from_degrees(96),
+        NAUTICAL => Angle.from_degrees(102),
+        ASTRONOMICAL => Angle.from_degrees(108)
+      }.freeze
+
+      PERIODS_OF_THE_DAY = [
+        MORNING = :morning,
+        EVENING = :evening
+      ].freeze
+
+      attr_reader :morning_civil_twilight_time,
+        :evening_civil_twilight_time,
+        :morning_nautical_twilight_time,
+        :evening_nautical_twilight_time,
+        :morning_astronomical_twilight_time,
+        :evening_astronomical_twilight_time
+
+      def initialize(observer:, sun:)
+        @observer = observer
+        @sun = sun
+        PERIODS_OF_THE_DAY.each do |period_of_the_day|
+          TWILIGHT_ANGLES.each do |twilight, _|
+            compute(period_of_the_day, twilight)
+          end
+        end
+      end
+
+      private
+
+      # Source:
+      #  Title: Practical Astronomy with your Calculator or Spreadsheet
+      #  Authors: Peter Duffett-Smith and Jonathan Zwart
+      #  Edition: Cambridge University Press
+      #  Chapter: 50 - Twilight
+      def compute(period_of_the_day, twilight)
+        period_time = if period_of_the_day == MORNING
+          observation_events.rising_time
+        else
+          observation_events.setting_time
+        end
+
+        hour_angle_at_period = equatorial_coordinates_at_midday
+          .compute_hour_angle(time: period_time, longitude: @observer.longitude)
+
+        zenith_angle = TWILIGHT_ANGLES[twilight]
+
+        term1 = zenith_angle.cos -
+          @observer.latitude.sin *
+            @equatorial_coordinates_at_midday.declination.sin
+        term2 = @observer.latitude.cos *
+          equatorial_coordinates_at_midday.declination.cos
+        hour_angle_ratio_at_twilight = term1 / term2
+
+        unless hour_angle_ratio_at_twilight.between?(-1, 1)
+          return instance_variable_set(
+            :"@#{period_of_the_day}_#{twilight}_twilight_time",
+            nil
+          )
+        end
+
+        hour_angle_at_twilight = Angle.acos(hour_angle_ratio_at_twilight)
+        time_sign = -1
+
+        if period_of_the_day == MORNING
+          hour_angle_at_twilight =
+            Angle.from_degrees(360 - hour_angle_at_twilight.degrees)
+          time_sign = 1
+        end
+
+        twilight_in_hours =
+          time_sign * (hour_angle_at_twilight - hour_angle_at_period).hours *
+          GreenwichSiderealTime::SIDEREAL_MINUTE_IN_UT_MINUTE
+        twilight_in_seconds = time_sign * twilight_in_hours * 3600
+
+        instance_variable_set(
+          :"@#{period_of_the_day}_#{twilight}_twilight_time",
+          (period_time + twilight_in_seconds).round
+        )
+      end
+
+      def observation_events
+        @observation_events ||= @sun.observation_events(observer: @observer)
+      end
+
+      def midday
+        utc_from_epoch = Epoch.to_utc(@sun.epoch)
+        Time.utc(
+          utc_from_epoch.year,
+          utc_from_epoch.month,
+          utc_from_epoch.day,
+          12
+        )
+      end
+
+      def equatorial_coordinates_at_midday
+        @equatorial_coordinates_at_midday ||=
+          @sun.apparent_ecliptic_coordinates
+            .to_apparent_equatorial(epoch: Epoch.from_time(midday))
+      end
+    end
+  end
+end
diff --git a/spec/astronoby/bodies/sun_spec.rb b/spec/astronoby/bodies/sun_spec.rb
index 00595df..1401547 100644
--- a/spec/astronoby/bodies/sun_spec.rb
+++ b/spec/astronoby/bodies/sun_spec.rb
@@ -677,286 +677,6 @@
     end
   end
 
-  describe "#morning_civil_twilight_time" do
-    it "returns a time" do
-      epoch = Astronoby::Epoch.from_time(Time.new)
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.zero,
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.morning_civil_twilight_time(observer: observer))
-        .to be_a Time
-    end
-
-    it "returns when the morning civil twilight starts" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_degrees(52),
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.morning_civil_twilight_time(observer: observer))
-        .to eq Time.utc(1979, 9, 7, 4, 44, 23)
-      # Time from IMCCE: 04:46
-    end
-
-    it "returns when the morning civil twilight starts" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
-        longitude: Astronoby::Angle.from_dms(151, 12, 26)
-      )
-
-      expect(sun.morning_civil_twilight_time(observer: observer))
-        .to eq Time.utc(2024, 3, 14, 19, 25, 38)
-      # Time from IMCCE: 19:29:29
-    end
-  end
-
-  describe "#evening_civil_twilight_time" do
-    it "returns a time" do
-      epoch = Astronoby::Epoch.from_time(Time.new)
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.zero,
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.evening_civil_twilight_time(observer: observer))
-        .to be_a Time
-    end
-
-    it "returns when the evening civil twilight ends" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_degrees(52),
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.evening_civil_twilight_time(observer: observer))
-        .to eq Time.utc(1979, 9, 7, 19, 8, 22)
-      # Time from IMCCE: 19:10
-    end
-
-    it "returns when the evening civil twilight ends" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
-        longitude: Astronoby::Angle.from_dms(151, 12, 26)
-      )
-
-      expect(sun.evening_civil_twilight_time(observer: observer))
-        .to eq Time.utc(2024, 3, 14, 8, 38, 28)
-      # Time from IMCCE: 08:39:23
-    end
-  end
-
-  describe "#morning_nautical_twilight_time" do
-    it "returns a time" do
-      epoch = Astronoby::Epoch.from_time(Time.new)
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.zero,
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.morning_nautical_twilight_time(observer: observer))
-        .to be_a Time
-    end
-
-    it "returns when the morning nautical twilight starts" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_degrees(52),
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.morning_nautical_twilight_time(observer: observer))
-        .to eq Time.utc(1979, 9, 7, 4, 2, 11)
-      # Time from IMCCE: 04:03
-    end
-
-    it "returns when the morning nautical twilight starts" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
-        longitude: Astronoby::Angle.from_dms(151, 12, 26)
-      )
-
-      expect(sun.morning_nautical_twilight_time(observer: observer))
-        .to eq Time.utc(2024, 3, 14, 18, 56, 26)
-      # Time from IMCCE: 19:00:13
-    end
-  end
-
-  describe "#evening_nautical_twilight_time" do
-    it "returns a time" do
-      epoch = Astronoby::Epoch.from_time(Time.new)
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.zero,
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.evening_nautical_twilight_time(observer: observer))
-        .to be_a Time
-    end
-
-    it "returns when the evening nautical twilight ends" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_degrees(52),
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.evening_nautical_twilight_time(observer: observer))
-        .to eq Time.utc(1979, 9, 7, 19, 50, 34)
-      # Time from IMCCE: 19:52
-    end
-
-    it "returns when the evening nautical twilight ends" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
-        longitude: Astronoby::Angle.from_dms(151, 12, 26)
-      )
-
-      expect(sun.evening_nautical_twilight_time(observer: observer))
-        .to eq Time.utc(2024, 3, 14, 9, 7, 39)
-      # Time from IMCCE: 09:08:37
-    end
-  end
-
-  describe "#morning_astronomical_twilight_time" do
-    it "returns a time" do
-      epoch = Astronoby::Epoch.from_time(Time.new)
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.zero,
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.morning_astronomical_twilight_time(observer: observer))
-        .to be_a Time
-    end
-
-    # Source:
-    #  Title: Practical Astronomy with your Calculator or Spreadsheet
-    #  Authors: Peter Duffett-Smith and Jonathan Zwart
-    #  Edition: Cambridge University Press
-    #  Chapter: 50 - Twilight, p.114
-    it "returns when the morning astronomical twilight starts" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_degrees(52),
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.morning_astronomical_twilight_time(observer: observer))
-        .to eq Time.utc(1979, 9, 7, 3, 16, 13)
-      # Time from Practical Astronomy: 03:12
-      # Time from IMCCE: 03:17
-    end
-
-    it "returns when the morning astronomical twilight starts" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
-        longitude: Astronoby::Angle.from_dms(151, 12, 26)
-      )
-
-      expect(sun.morning_astronomical_twilight_time(observer: observer))
-        .to eq Time.utc(2024, 3, 14, 18, 26, 47)
-      # Time from IMCCE: 18:30:31
-    end
-
-    context "when the twilight never ends" do
-      it "returns nil" do
-        epoch = Astronoby::Epoch.from_time(Time.utc(2024, 6, 20))
-        sun = described_class.new(epoch: epoch)
-        observer = Astronoby::Observer.new(
-          latitude: Astronoby::Angle.from_degrees(65),
-          longitude: Astronoby::Angle.zero
-        )
-
-        expect(sun.morning_astronomical_twilight_time(observer: observer))
-          .to be_nil
-      end
-    end
-  end
-
-  describe "#evening_astronomical_twilight_time" do
-    it "returns a time" do
-      epoch = Astronoby::Epoch.from_time(Time.new)
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.zero,
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.evening_astronomical_twilight_time(observer: observer))
-        .to be_a Time
-    end
-
-    # Source:
-    #  Title: Practical Astronomy with your Calculator or Spreadsheet
-    #  Authors: Peter Duffett-Smith and Jonathan Zwart
-    #  Edition: Cambridge University Press
-    #  Chapter: 50 - Twilight, p.114
-    it "returns when the evening astronomical twilight ends" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_degrees(52),
-        longitude: Astronoby::Angle.zero
-      )
-
-      expect(sun.evening_astronomical_twilight_time(observer: observer))
-        .to eq Time.utc(1979, 9, 7, 20, 36, 33)
-      # Time from Practical Astronomy: 20:43
-      # Time from IMCCE: 20:37
-    end
-
-    it "returns when the evening astronomical twilight ends" do
-      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
-      sun = described_class.new(epoch: epoch)
-      observer = Astronoby::Observer.new(
-        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
-        longitude: Astronoby::Angle.from_dms(151, 12, 26)
-      )
-
-      expect(sun.evening_astronomical_twilight_time(observer: observer))
-        .to eq Time.utc(2024, 3, 14, 9, 37, 18)
-      # Time from IMCCE: 09:38:17
-    end
-
-    context "when the twilight never ends" do
-      it "returns nil" do
-        epoch = Astronoby::Epoch.from_time(Time.utc(2024, 6, 20))
-        sun = described_class.new(epoch: epoch)
-        observer = Astronoby::Observer.new(
-          latitude: Astronoby::Angle.from_degrees(65),
-          longitude: Astronoby::Angle.zero
-        )
-
-        expect(sun.evening_astronomical_twilight_time(observer: observer))
-          .to be_nil
-      end
-    end
-  end
-
   describe "::equation_of_time" do
     it "returns an Integer" do
       date = Date.new
diff --git a/spec/astronoby/events/twilight_events_spec.rb b/spec/astronoby/events/twilight_events_spec.rb
new file mode 100644
index 0000000..d2f06af
--- /dev/null
+++ b/spec/astronoby/events/twilight_events_spec.rb
@@ -0,0 +1,351 @@
+# frozen_string_literal: true
+
+RSpec.describe Astronoby::Events::TwilightEvents do
+  describe "#morning_civil_twilight_time" do
+    it "returns a time" do
+      epoch = Astronoby::Epoch.from_time(Date.new)
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.zero,
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.morning_civil_twilight_time).to be_a(Time)
+    end
+
+    it "returns when the morning civil twilight starts" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_degrees(52),
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.morning_civil_twilight_time)
+        .to eq Time.utc(1979, 9, 7, 4, 44, 23)
+      # Time from IMCCE: 04:46
+    end
+
+    it "returns when the morning civil twilight starts" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
+        longitude: Astronoby::Angle.from_dms(151, 12, 26)
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.morning_civil_twilight_time)
+        .to eq Time.utc(2024, 3, 14, 19, 25, 38)
+      # Time from IMCCE: 19:29:29
+    end
+
+    context "when the civil twilight doesn't start" do
+      it "returns nil" do
+        epoch = Astronoby::Epoch.from_time(Time.utc(2024, 6, 20))
+        sun = Astronoby::Sun.new(epoch: epoch)
+        observer = Astronoby::Observer.new(
+          latitude: Astronoby::Angle.from_degrees(65),
+          longitude: Astronoby::Angle.zero
+        )
+        twilight_events = described_class.new(observer: observer, sun: sun)
+
+        expect(twilight_events.morning_civil_twilight_time).to be_nil
+      end
+    end
+  end
+
+  describe "#evening_civil_twilight_time" do
+    it "returns a time" do
+      epoch = Astronoby::Epoch.from_time(Date.new)
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.zero,
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.evening_civil_twilight_time).to be_a(Time)
+    end
+
+    it "returns when the evening civil twilight ends" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_degrees(52),
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.evening_civil_twilight_time)
+        .to eq Time.utc(1979, 9, 7, 19, 8, 22)
+      # Time from IMCCE: 19:10
+    end
+
+    it "returns when the evening civil twilight ends" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
+        longitude: Astronoby::Angle.from_dms(151, 12, 26)
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.evening_civil_twilight_time)
+        .to eq Time.utc(2024, 3, 14, 8, 38, 28)
+      # Time from IMCCE: 08:39:23
+    end
+
+    context "when the civil twilight doesn't start" do
+      it "returns nil" do
+        epoch = Astronoby::Epoch.from_time(Time.utc(2024, 6, 20))
+        sun = Astronoby::Sun.new(epoch: epoch)
+        observer = Astronoby::Observer.new(
+          latitude: Astronoby::Angle.from_degrees(65),
+          longitude: Astronoby::Angle.zero
+        )
+        twilight_events = described_class.new(observer: observer, sun: sun)
+
+        expect(twilight_events.evening_civil_twilight_time).to be_nil
+      end
+    end
+  end
+
+  describe "#morning_nautical_twilight_time" do
+    it "returns a time" do
+      epoch = Astronoby::Epoch.from_time(Date.new)
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.zero,
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.morning_nautical_twilight_time).to be_a(Time)
+    end
+
+    it "returns when the morning nautical twilight starts" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_degrees(52),
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.morning_nautical_twilight_time)
+        .to eq Time.utc(1979, 9, 7, 4, 2, 11)
+      # Time from IMCCE: 04:03
+    end
+
+    it "returns when the morning nautical twilight starts" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
+        longitude: Astronoby::Angle.from_dms(151, 12, 26)
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.morning_nautical_twilight_time)
+        .to eq Time.utc(2024, 3, 14, 18, 56, 26)
+      # Time from IMCCE: 19:00:13
+    end
+
+    context "when the nautical twilight doesn't start" do
+      it "returns nil" do
+        epoch = Astronoby::Epoch.from_time(Time.utc(2024, 6, 20))
+        sun = Astronoby::Sun.new(epoch: epoch)
+        observer = Astronoby::Observer.new(
+          latitude: Astronoby::Angle.from_degrees(55),
+          longitude: Astronoby::Angle.zero
+        )
+        twilight_events = described_class.new(observer: observer, sun: sun)
+
+        expect(twilight_events.morning_nautical_twilight_time).to be_nil
+      end
+    end
+  end
+
+  describe "#evening_nautical_twilight_time" do
+    it "returns a time" do
+      epoch = Astronoby::Epoch.from_time(Date.new)
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.zero,
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.evening_nautical_twilight_time).to be_a(Time)
+    end
+
+    it "returns when the evening nautical twilight ends" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_degrees(52),
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.evening_nautical_twilight_time)
+        .to eq Time.utc(1979, 9, 7, 19, 50, 34)
+      # Time from IMCCE: 19:52
+    end
+
+    it "returns when the evening nautical twilight ends" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
+        longitude: Astronoby::Angle.from_dms(151, 12, 26)
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.evening_nautical_twilight_time)
+        .to eq Time.utc(2024, 3, 14, 9, 7, 39)
+      # Time from IMCCE: 09:08:37
+    end
+
+    context "when the nautical twilight doesn't start" do
+      it "returns nil" do
+        epoch = Astronoby::Epoch.from_time(Time.utc(2024, 6, 20))
+        sun = Astronoby::Sun.new(epoch: epoch)
+        observer = Astronoby::Observer.new(
+          latitude: Astronoby::Angle.from_degrees(55),
+          longitude: Astronoby::Angle.zero
+        )
+        twilight_events = described_class.new(observer: observer, sun: sun)
+
+        expect(twilight_events.evening_nautical_twilight_time).to be_nil
+      end
+    end
+  end
+
+  describe "#morning_astronomical_twilight_time" do
+    it "returns a time" do
+      epoch = Astronoby::Epoch.from_time(Date.new)
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.zero,
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.morning_astronomical_twilight_time).to be_a(Time)
+    end
+
+    # Source:
+    #  Title: Practical Astronomy with your Calculator or Spreadsheet
+    #  Authors: Peter Duffett-Smith and Jonathan Zwart
+    #  Edition: Cambridge University Press
+    #  Chapter: 50 - Twilight, p.114
+    it "returns when the morning astronomical twilight starts" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_degrees(52),
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.morning_astronomical_twilight_time)
+        .to eq Time.utc(1979, 9, 7, 3, 16, 13)
+      # Time from Practical Astronomy: 03:12
+      # Time from IMCCE: 03:17
+    end
+
+    it "returns when the morning astronomical twilight starts" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
+        longitude: Astronoby::Angle.from_dms(151, 12, 26)
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.morning_astronomical_twilight_time)
+        .to eq Time.utc(2024, 3, 14, 18, 26, 47)
+      # Time from IMCCE: 18:30:31
+    end
+
+    context "when the astronomical twilight doesn't start" do
+      it "returns nil" do
+        epoch = Astronoby::Epoch.from_time(Time.utc(2024, 6, 20))
+        sun = Astronoby::Sun.new(epoch: epoch)
+        observer = Astronoby::Observer.new(
+          latitude: Astronoby::Angle.from_degrees(49),
+          longitude: Astronoby::Angle.zero
+        )
+        twilight_events = described_class.new(observer: observer, sun: sun)
+
+        expect(twilight_events.morning_astronomical_twilight_time).to be_nil
+      end
+    end
+  end
+
+  describe "#evening_astronomical_twilight_time" do
+    it "returns a time" do
+      epoch = Astronoby::Epoch.from_time(Date.new)
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.zero,
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.evening_astronomical_twilight_time).to be_a(Time)
+    end
+
+    # Source:
+    #  Title: Practical Astronomy with your Calculator or Spreadsheet
+    #  Authors: Peter Duffett-Smith and Jonathan Zwart
+    #  Edition: Cambridge University Press
+    #  Chapter: 50 - Twilight, p.114
+    it "returns when the evening astronomical twilight ends" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(1979, 9, 7))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_degrees(52),
+        longitude: Astronoby::Angle.zero
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.evening_astronomical_twilight_time)
+        .to eq Time.utc(1979, 9, 7, 20, 36, 33)
+      # Time from Practical Astronomy: 20:43
+      # Time from IMCCE: 20:37
+    end
+
+    it "returns when the evening astronomical twilight ends" do
+      epoch = Astronoby::Epoch.from_time(Time.utc(2024, 3, 14))
+      sun = Astronoby::Sun.new(epoch: epoch)
+      observer = Astronoby::Observer.new(
+        latitude: Astronoby::Angle.from_dms(-33, 52, 4),
+        longitude: Astronoby::Angle.from_dms(151, 12, 26)
+      )
+      twilight_events = described_class.new(observer: observer, sun: sun)
+
+      expect(twilight_events.evening_astronomical_twilight_time)
+        .to eq Time.utc(2024, 3, 14, 9, 37, 18)
+      # Time from IMCCE: 09:38:17
+    end
+
+    context "when the astronomical twilight doesn't start" do
+      it "returns nil" do
+        epoch = Astronoby::Epoch.from_time(Time.utc(2024, 6, 20))
+        sun = Astronoby::Sun.new(epoch: epoch)
+        observer = Astronoby::Observer.new(
+          latitude: Astronoby::Angle.from_degrees(49),
+          longitude: Astronoby::Angle.zero
+        )
+        twilight_events = described_class.new(observer: observer, sun: sun)
+
+        expect(twilight_events.evening_astronomical_twilight_time).to be_nil
+      end
+    end
+  end
+end