diff --git a/doc/api/index.rst b/doc/api/index.rst
index 58a41dd8cec..157e2921873 100644
--- a/doc/api/index.rst
+++ b/doc/api/index.rst
@@ -38,6 +38,7 @@ Plotting data and laying out the map:
     Figure.plot3d
     Figure.set_panel
     Figure.shift_origin
+    Figure.solar
     Figure.subplot
     Figure.text
 
diff --git a/examples/gallery/embellishments/solar.py b/examples/gallery/embellishments/solar.py
new file mode 100644
index 00000000000..fdfb335630b
--- /dev/null
+++ b/examples/gallery/embellishments/solar.py
@@ -0,0 +1,46 @@
+"""
+Day-night terminator line and twilights
+---------------------------------------
+
+Use :meth:`pygmt.Figure.solar` to plot the day-night terminator line, 
+and civil, nautical, astronomical twilights.
+"""
+import datetime
+
+import pygmt
+
+fig = pygmt.Figure()
+# Create a figure showing the global region on a Mollweide projection
+# Land color is set to dark green and water color is set to light blue
+fig.coast(region="d", projection="W0/15c", land="darkgreen", water="lightblue")
+# Set a time for the day-night terminator and twilights, 1700 UTC on January 1, 2000
+terminator_datetime = datetime.datetime(
+    year=2000, month=1, day=1, hour=17, minute=0, second=0
+)
+# Set the pen line to be 1p thick
+# Set the fill for the night area to be navy blue at different transparency levels
+fig.solar(
+    terminator="day_night",
+    terminator_datetime=terminator_datetime,
+    fill="navyblue@95",
+    pen="0.5p",
+)
+fig.solar(
+    terminator="civil",
+    terminator_datetime=terminator_datetime,
+    fill="navyblue@85",
+    pen="0.5p",
+)
+fig.solar(
+    terminator="nautical",
+    terminator_datetime=terminator_datetime,
+    fill="navyblue@80",
+    pen="0.5p",
+)
+fig.solar(
+    terminator="astronomical",
+    terminator_datetime=terminator_datetime,
+    fill="navyblue@80",
+    pen="0.5p",
+)
+fig.show()
diff --git a/pygmt/figure.py b/pygmt/figure.py
index acd448b9472..a8d89b1e727 100644
--- a/pygmt/figure.py
+++ b/pygmt/figure.py
@@ -391,6 +391,7 @@ def _repr_html_(self):
         plot,
         plot3d,
         set_panel,
+        solar,
         subplot,
         text,
     )
diff --git a/pygmt/src/__init__.py b/pygmt/src/__init__.py
index 93930a3a55c..60dd1ed0e15 100644
--- a/pygmt/src/__init__.py
+++ b/pygmt/src/__init__.py
@@ -25,6 +25,7 @@
 from pygmt.src.meca import meca
 from pygmt.src.plot import plot
 from pygmt.src.plot3d import plot3d
+from pygmt.src.solar import solar
 from pygmt.src.subplot import set_panel, subplot
 from pygmt.src.surface import surface
 from pygmt.src.text import text_ as text  # "text" is an argument within "text_"
diff --git a/pygmt/src/solar.py b/pygmt/src/solar.py
new file mode 100644
index 00000000000..aa621abc6f6
--- /dev/null
+++ b/pygmt/src/solar.py
@@ -0,0 +1,99 @@
+"""
+solar - Plot day-night terminators.
+"""
+
+import datetime
+
+import pandas as pd
+from pygmt.clib import Session
+from pygmt.exceptions import GMTInvalidInput
+from pygmt.helpers import build_arg_string, fmt_docstring, kwargs_to_strings, use_alias
+
+
+@fmt_docstring
+@use_alias(
+    B="frame",
+    G="fill",
+    J="projection",
+    R="region",
+    U="timestamp",
+    V="verbose",
+    W="pen",
+    X="xshift",
+    Y="yshift",
+    c="panel",
+    p="perspective",
+    t="transparency",
+)
+@kwargs_to_strings(R="sequence", c="sequence_comma", p="sequence")
+def solar(self, terminator="d", terminator_datetime=None, **kwargs):
+    r"""
+    Plot day-light terminators.
+
+    This function plots the day-night terminator. Additionally, it can
+    plot the terminators for civil twilight, nautical twilight, and
+    astronomical twilight.
+
+    Full parameter list at :gmt-docs:`solar.html`
+
+    {aliases}
+
+    Parameters
+    ----------
+    terminator : str
+        Set the type of terminator displayed. Valid arguments are
+        **day_night**, **civil**, **nautical**, and **astronomical**, which
+        can be set with either the full name or the first letter of the name.
+        [Default is **day_night**]
+    terminator_datetime : str or datetime object
+        Set the UTC date and time of the displayed terminator. It can be
+        passed as a string or a datetime object.
+        [Default is the current UTC date and time]
+    {R}
+    {J}
+    {B}
+    fill : str
+        Color or pattern for filling of terminators.
+    pen : str
+        Set pen attributes for lines. The default pen
+        is ``default,black,solid``.
+    {U}
+    {V}
+    {XY}
+    {c}
+    {p}
+    {t}
+    """
+    # TODO: Incorporate "-T+zTZ"
+
+    kwargs = self._preprocess(**kwargs)  # pylint: disable=protected-access
+    if "T" in kwargs:
+        raise GMTInvalidInput(
+            "Use 'terminator' and 'terminator_datetime' instead of 'T'."
+        )
+    if terminator not in [
+        "day_night",
+        "nautical",
+        "civil",
+        "astronomical",
+        "astro",
+        "d",
+        "n",
+        "c",
+        "a",
+    ]:
+        raise GMTInvalidInput(
+            f"Unrecognized solar terminator type '{terminator}'. Valid values "
+            "are 'day_night', 'civil', 'nautical', and 'astronomical'."
+        )
+    kwargs["T"] = terminator[0]
+    if terminator_datetime:
+        try:
+            datetime_string = pd.to_datetime(terminator_datetime).strftime(
+                "%Y-%m-%dT%H:%M:%S.%f"
+            )
+        except ValueError as verr:
+            raise GMTInvalidInput("Unrecognized datetime format.") from verr
+        kwargs["T"] += f"+d{datetime_string}"
+    with Session() as lib:
+        lib.call_module("solar", build_arg_string(kwargs))
diff --git a/pygmt/tests/baseline/test_coast.png b/pygmt/tests/baseline/test_coast.png
deleted file mode 100644
index 9a31355f638..00000000000
Binary files a/pygmt/tests/baseline/test_coast.png and /dev/null differ
diff --git a/pygmt/tests/baseline/test_coast.png.dvc b/pygmt/tests/baseline/test_coast.png.dvc
new file mode 100644
index 00000000000..dc66fee1240
--- /dev/null
+++ b/pygmt/tests/baseline/test_coast.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: a054a1df3a6eb6f6799ba0fc104ade45
+  size: 135451
+  path: test_coast.png
diff --git a/pygmt/tests/baseline/test_coast_aliases.png b/pygmt/tests/baseline/test_coast_aliases.png
deleted file mode 100644
index 25d33a151cd..00000000000
Binary files a/pygmt/tests/baseline/test_coast_aliases.png and /dev/null differ
diff --git a/pygmt/tests/baseline/test_coast_aliases.png.dvc b/pygmt/tests/baseline/test_coast_aliases.png.dvc
new file mode 100644
index 00000000000..6f168b0088c
--- /dev/null
+++ b/pygmt/tests/baseline/test_coast_aliases.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: d53aa16264ebd5ae546c95b88855b16a
+  size: 519870
+  path: test_coast_aliases.png
diff --git a/pygmt/tests/baseline/test_coast_dcw_continent.png.dvc b/pygmt/tests/baseline/test_coast_dcw_continent.png.dvc
new file mode 100644
index 00000000000..e19bc1edcf8
--- /dev/null
+++ b/pygmt/tests/baseline/test_coast_dcw_continent.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: 479f5ea4fb662289c4bf0e9fc1d4ae4b
+  size: 91352
+  path: test_coast_dcw_continent.png
diff --git a/pygmt/tests/baseline/test_coast_dcw_list.png.dvc b/pygmt/tests/baseline/test_coast_dcw_list.png.dvc
new file mode 100644
index 00000000000..28c7e8d07b3
--- /dev/null
+++ b/pygmt/tests/baseline/test_coast_dcw_list.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: 30c3f4c90ba740b7d9edae97d9d3b853
+  size: 93411
+  path: test_coast_dcw_list.png
diff --git a/pygmt/tests/baseline/test_coast_dcw_multiple.png.dvc b/pygmt/tests/baseline/test_coast_dcw_multiple.png.dvc
new file mode 100644
index 00000000000..5bd0798c1da
--- /dev/null
+++ b/pygmt/tests/baseline/test_coast_dcw_multiple.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: c68c4ecaffdda779a6b20aba786dd919
+  size: 94025
+  path: test_coast_dcw_multiple.png
diff --git a/pygmt/tests/baseline/test_coast_dcw_single.png.dvc b/pygmt/tests/baseline/test_coast_dcw_single.png.dvc
new file mode 100644
index 00000000000..38a0b2b1a5d
--- /dev/null
+++ b/pygmt/tests/baseline/test_coast_dcw_single.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: 40fcf70e1f73ba2be60cbf9e3f15794d
+  size: 83794
+  path: test_coast_dcw_single.png
diff --git a/pygmt/tests/baseline/test_coast_dcw_state.png.dvc b/pygmt/tests/baseline/test_coast_dcw_state.png.dvc
new file mode 100644
index 00000000000..4710974e8f7
--- /dev/null
+++ b/pygmt/tests/baseline/test_coast_dcw_state.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: faddbe172a81a10563eebf75744d7339
+  size: 110297
+  path: test_coast_dcw_state.png
diff --git a/pygmt/tests/baseline/test_coast_iceland.png b/pygmt/tests/baseline/test_coast_iceland.png
deleted file mode 100644
index 14a33962956..00000000000
Binary files a/pygmt/tests/baseline/test_coast_iceland.png and /dev/null differ
diff --git a/pygmt/tests/baseline/test_coast_iceland.png.dvc b/pygmt/tests/baseline/test_coast_iceland.png.dvc
new file mode 100644
index 00000000000..d71d76861b0
--- /dev/null
+++ b/pygmt/tests/baseline/test_coast_iceland.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: c4efb846d4f0a26c7c3b4900ae0043bf
+  size: 23420
+  path: test_coast_iceland.png
diff --git a/pygmt/tests/baseline/test_coast_world_mercator.png b/pygmt/tests/baseline/test_coast_world_mercator.png
deleted file mode 100644
index 27f9b16fd57..00000000000
Binary files a/pygmt/tests/baseline/test_coast_world_mercator.png and /dev/null differ
diff --git a/pygmt/tests/baseline/test_coast_world_mercator.png.dvc b/pygmt/tests/baseline/test_coast_world_mercator.png.dvc
new file mode 100644
index 00000000000..d77e879dca1
--- /dev/null
+++ b/pygmt/tests/baseline/test_coast_world_mercator.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: 12884b768aa463d575019347dedfa6b0
+  size: 322546
+  path: test_coast_world_mercator.png
diff --git a/pygmt/tests/baseline/test_solar_default_terminator.png.dvc b/pygmt/tests/baseline/test_solar_default_terminator.png.dvc
new file mode 100644
index 00000000000..6bc9e740fff
--- /dev/null
+++ b/pygmt/tests/baseline/test_solar_default_terminator.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: 0a7f4959b500b6fa3a560a6368db0f90
+  size: 25982
+  path: test_solar_default_terminator.png
diff --git a/pygmt/tests/baseline/test_solar_set_terminator_datetime_object.png.dvc b/pygmt/tests/baseline/test_solar_set_terminator_datetime_object.png.dvc
new file mode 100644
index 00000000000..61b633b93ca
--- /dev/null
+++ b/pygmt/tests/baseline/test_solar_set_terminator_datetime_object.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: 0a7f4959b500b6fa3a560a6368db0f90
+  size: 25982
+  path: test_solar_set_terminator_datetime_object.png
diff --git a/pygmt/tests/baseline/test_solar_set_terminator_datetime_string.png.dvc b/pygmt/tests/baseline/test_solar_set_terminator_datetime_string.png.dvc
new file mode 100644
index 00000000000..a35368bbb45
--- /dev/null
+++ b/pygmt/tests/baseline/test_solar_set_terminator_datetime_string.png.dvc
@@ -0,0 +1,4 @@
+outs:
+- md5: 9437b5fd846526c7cac12ab327a4d78f
+  size: 26501
+  path: test_solar_set_terminator_datetime_string.png
diff --git a/pygmt/tests/test_coast.py b/pygmt/tests/test_coast.py
index 69635aa30f6..f1df26bfccd 100644
--- a/pygmt/tests/test_coast.py
+++ b/pygmt/tests/test_coast.py
@@ -1,5 +1,5 @@
 """
-Tests for coast.
+Tests for fig.coast.
 """
 import pytest
 from pygmt import Figure
@@ -14,60 +14,37 @@ def test_coast():
     """
     fig = Figure()
     fig.coast(
-        R="-30/30/-40/40",
-        J="m0.1i",
-        B=5,
-        I="1/1p,blue",
-        N="1/0.25p,-",
-        W="0.25p,white",
-        G="green",
-        S="blue",
-        D="c",
-        A=10000,
+        region="-30/30/-40/40",
+        projection="m0.1i",
+        frame=5,
+        rivers="1/1p,blue",
+        borders="1/0.25p,-",
+        shorelines="0.25p,white",
+        land="green",
+        water="blue",
+        resolution="c",
+        area_thresh=10000,
     )
     return fig
 
 
-@check_figures_equal()
+@pytest.mark.mpl_image_compare
 def test_coast_iceland():
     """
-    Test passing in R as a list.
+    Test passing in region as a list.
     """
-    fig_ref, fig_test = Figure(), Figure()
-    # Use single-character arguments for the reference image
-    fig_ref.coast(R="-30/-10/60/65", J="m1c", B="", G="p28+r100")
-    fig_test.coast(
-        region=[-30, -10, 60, 65], projection="m1c", frame=True, land="p28+r100"
-    )
-    return fig_ref, fig_test
+    fig = Figure()
+    fig.coast(region=[-30, -10, 60, 65], projection="m1c", frame=True, land="p28+r100")
+    return fig
 
 
-@check_figures_equal()
+@pytest.mark.mpl_image_compare
 def test_coast_aliases():
     """
     Test that all aliases work.
     """
-    fig_ref, fig_test = Figure(), Figure()
-    fig_ref.coast(
-        R="-30/30/-40/40",
-        J="M25c",
-        B="afg",
-        I="1/1p,black",
-        N="1/0.5p,-",
-        W="0.25p,white",
-        G="moccasin",
-        S="skyblue",
-        D="i",
-        A=1000,
-        L="jCM+c1+w1000k+f+l",
-        X="a4c",
-        Y="a10c",
-        p="135/25",
-        t=13,
-        E="MA+gred",
-        C="blue",
-    )
-    fig_test.coast(
+    fig = Figure()
+    fig.coast(
         region=[-30, 30, -40, 40],  # R
         projection="M25c",  # J
         frame="afg",  # B
@@ -86,7 +63,7 @@ def test_coast_aliases():
         dcw="MA+gred",  # E
         lakes="blue",  # C
     )
-    return fig_ref, fig_test
+    return fig
 
 
 @pytest.mark.mpl_image_compare
@@ -115,99 +92,81 @@ def test_coast_required_args():
         fig.coast(region="EG")
 
 
-@check_figures_equal()
+@pytest.mark.mpl_image_compare
 def test_coast_dcw_single():
     """
     Test passing a single country code to dcw.
     """
-    fig_ref, fig_test = Figure(), Figure()
-    # Use single-character arguments for the reference image
-    fig_ref.coast(R="-10/15/25/44", J="M15c", B="a", G="brown", E="ES+gbisque+pblue")
-    fig_test.coast(
+    fig = Figure()
+    fig.coast(
         region=[-10, 15, 25, 44],
         frame="a",
         projection="M15c",
         land="brown",
         dcw="ES+gbisque+pblue",
     )
-    return fig_ref, fig_test
+    return fig
 
 
-@check_figures_equal()
+@pytest.mark.mpl_image_compare
 def test_coast_dcw_multiple():
     """
     Test passing multiple country code to dcw.
     """
-    fig_ref, fig_test = Figure(), Figure()
-    # Use single-character arguments for the reference image
-    fig_ref.coast(R="-10/15/25/44", J="M15c", B="a", G="brown", E="ES,IT+gbisque+pblue")
-    fig_test.coast(
+    fig = Figure()
+    fig.coast(
         region=[-10, 15, 25, 44],
         frame="a",
         projection="M15c",
         land="brown",
         dcw="ES,IT+gbisque+pblue",
     )
-    return fig_ref, fig_test
+    return fig
 
 
-@check_figures_equal()
+@pytest.mark.mpl_image_compare
 def test_coast_dcw_list():
     """
     Test passing a list of country codes and fill options to dcw.
     """
-    fig_ref, fig_test = Figure(), Figure()
-    # Use single-character arguments for the reference image
-    fig_ref.coast(
-        R="-10/15/25/44",
-        J="M15c",
-        B="a",
-        G="brown",
-        E=["ES+gbisque+pgreen", "IT+gcyan+pblue"],
-    )
-    fig_test.coast(
+    fig = Figure()
+    fig.coast(
         region=[-10, 15, 25, 44],
         frame="a",
         projection="M15c",
         land="brown",
         dcw=["ES+gbisque+pgreen", "IT+gcyan+pblue"],
     )
-    return fig_ref, fig_test
+    return fig
 
 
-@check_figures_equal()
+@pytest.mark.mpl_image_compare
 def test_coast_dcw_continent():
     """
     Test passing a continent code to dcw.
     """
-    fig_ref, fig_test = Figure(), Figure()
-    # Use single-character arguments for the reference image
-    fig_ref.coast(R="-10/15/25/44", J="M15c", B="a", G="brown", E="=AF+gbisque+pblue")
-    fig_test.coast(
+    fig = Figure()
+    fig.coast(
         region=[-10, 15, 25, 44],
         frame="a",
         projection="M15c",
         land="brown",
         dcw="=AF+gbisque+pblue",
     )
-    return fig_ref, fig_test
+    return fig
 
 
-@check_figures_equal()
+@pytest.mark.mpl_image_compare
 def test_coast_dcw_state():
     """
     Test passing a US state code to dcw.
     """
-    fig_ref, fig_test = Figure(), Figure()
-    # Use single-character arguments for the reference image
-    fig_ref.coast(
-        R="-75/-69/40/44", J="M15c", B="a", G="brown", E="US.MA+gbisque+pblue"
-    )
-    fig_test.coast(
+    fig = Figure()
+    fig.coast(
         region=[-75, -69, 40, 44],
         frame="a",
         projection="M15c",
         land="brown",
         dcw="US.MA+gbisque+pblue",
     )
-    return fig_ref, fig_test
+    return fig
diff --git a/pygmt/tests/test_solar.py b/pygmt/tests/test_solar.py
new file mode 100644
index 00000000000..adc2eb649a8
--- /dev/null
+++ b/pygmt/tests/test_solar.py
@@ -0,0 +1,102 @@
+"""
+Tests for solar.
+"""
+import datetime
+
+import pytest
+from pygmt import Figure
+from pygmt.exceptions import GMTInvalidInput
+
+
+@pytest.mark.mpl_image_compare
+def test_solar_set_terminator_datetime_string():
+    """
+    Test passing the solar argument with the civil terminator and a datetime
+    string.
+    """
+    fig = Figure()
+    fig.solar(
+        region="d",
+        projection="W0/15c",
+        frame="a",
+        terminator="civil",
+        terminator_datetime="1990-02-17 04:25:00",
+    )
+    return fig
+
+
+@pytest.mark.mpl_image_compare
+def test_solar_default_terminator():
+    """
+    Test passing the solar argument with a time string and no terminator type
+    to confirm the default terminator type.
+    """
+    fig = Figure()
+    fig.solar(
+        region="d",
+        projection="W0/15c",
+        frame="a",
+        terminator_datetime="1990-02-17 04:25:00",
+    )
+    return fig
+
+
+@pytest.mark.mpl_image_compare
+def test_solar_set_terminator_datetime_object():
+    """
+    Test passing the solar argument with the day_night terminator and a
+    datetime string.
+    """
+    fig = Figure()
+    terminator_datetime = datetime.datetime(
+        year=1990, month=2, day=17, hour=4, minute=25, second=0
+    )
+    fig.solar(
+        region="d",
+        projection="W0/15c",
+        frame="a",
+        terminator="day_night",
+        terminator_datetime=terminator_datetime,
+    )
+    return fig
+
+
+def test_invalid_terminator_type():
+    """
+    Test if solar fails when it receives an invalid terminator type.
+    """
+    fig = Figure()
+    with pytest.raises(GMTInvalidInput):
+        fig.solar(
+            region="d",
+            projection="W0/15c",
+            frame="a",
+            terminator="invalid",
+        )
+
+
+def test_invalid_T_parameter():
+    """
+    Test if solar fails when it receives a GMT argument for 'T' instead of the
+    PyGMT arguments for 'terminator' and 'terminator_datetime'.
+    """
+    fig = Figure()
+    with pytest.raises(GMTInvalidInput):
+        # Use single-letter option 'T' for testing
+        fig.solar(
+            region="d", projection="W0/15c", frame="a", T="d+d1990-02-17T04:25:00"
+        )
+
+
+def test_invalid_datetime():
+    """
+    Test if solar fails when it receives an invalid datetime string.
+    """
+    fig = Figure()
+    with pytest.raises(GMTInvalidInput):
+        fig.solar(
+            region="d",
+            projection="W0/15c",
+            frame="a",
+            terminator_datetime="199A-02-17 04:25:00",
+        )