Day-night terminator line and twilights

Use pygmt.Figure.solar to show the different transition stages between daytime and nighttime. The parameter terminator is used to set the twilight stage, and can be either "day_night" (brightest), "civil", "nautical", or "astronomical" (darkest). Refer to https://en.wikipedia.org/wiki/Twilight for more information.

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, 17:00 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 0.5 points 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()