Tracing across the 18°N parallel shows the subsolar point is, also, at 18°N on May 2. When using the analemma for north-south sun angle problems, the equation of time is irrelevant. The path of the Sun in the sky through the year, also, demonstrates this figure-eight shape. The analemma adds the equator of time that causes the figure-eight flip in the graph. The parallels south of the equator are southern latitudes, and those north of the equator are northern latitudes. The horizontal lines represent the parallels, and the intersection of the date-marked line of the figure eight with the parallel indicates the location of the direct rays or the subsolar point. The figure-eight shape of the analemma represents the changing position of the subsolar point as the Sun migrates between the Tropic of Cancer and the Tropic of Capricorn. Using the analemma, the subsolar point on August 2 is at 18°N.

Atmospheric scattering has a variety of effects beyond twilight and dawn including the blue color of the sky. Enormous electrical discharges result from the buildup of electrical energy polarity that light the sky, and these are called lightning, but this is not the cause of twilight and dawn. The circle of illumination is not a purely theoretical construct and in the absence of an atmosphere the boundary between sunlight and darkness is pronounced. The auroras light the sky only at high latitudes and intermittently, but this does not result in twilight and dawn. The solar wind does not disperse the light, but it can interact with the upper atmosphere and cause the aurora displays. The atmosphere scatters the light, to produce twilight and dawn and the beautiful sunsets that are experienced. Were it not for the atmosphere, when a location crossed the circle of illumination, it would result in darkness. Locations on Earth experience twilight and dawn, because the thick atmosphere of Earth scatters the light. To the east of the International Date Line is Monday, and to the west is Tuesday.

Monday will be disappearing at the International Date Line as the amount of Tuesday increases around the world. The beginning of the new day will be located at 30°W. The known time is to the east, so the unknown time will be earlier. The total longitude represents 7 time zones or seven hours difference in time. The difference in longitude is 105°, because 15☎ measures from the Prime Meridian, and 90°W is measuring the opposite direction from 0°. The longitude of both of the locations is a central meridian. A time zone is 15° wide, centered on the meridians that are multiples of 15°. Time is based on longitude, and clock time is rounded to the time at the nearest central meridian. The latitudes are irrelevant to calculations of relative time. Tuesday at 30°S, 15☎, the time and day at 30°N, 90°W will be 8 p.m. Without political considerations, if it is 3 a.m.

The Change by C.M. Meridian