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Antarctica sits on every line of longitude because the South Pole is on the continent. Theoretically, Antarctica would be located in all time zones; however, areas south of the Antarctic Circle experience extreme day-night cycles near the times of the June and December solstices, making it difficult to determine which time zone would be appropriate.
A mean solar day (what we normally measure as a "day") is the average time between local solar noons ("average" since this varies slightly over a year). Earth makes one rotation around its axis each sidereal day; during that time it moves a short distance (about 1°) along its orbit around the Sun.
The length of polar night varies by latitude from 24 hours just inside the polar circles to 179 days at the poles. As there are various kinds of twilight, there also exist various kinds of polar twilight that progress towards true polar night. Each kind of polar night is defined as when it is darker than the corresponding kind of twilight.
As an example, at the North Cape of Norway at midnight on June 21/22, the longitude of 25.9 degrees east makes the moment 103.2 minutes earlier by clock time; but the local time, 2 hours ahead of GMT in the summer, makes it 120 minutes later by clock time. The equation of time at that date is -2.0 minutes.
These observations can be used to determine changes in Earth's rotation over the last 27 centuries, since the length of the day is a critical parameter in the calculation of the place and time of eclipses. A change in day length of milliseconds per century shows up as a change of hours and thousands of kilometers in eclipse observations.
A simplified illustration of the relation between date line, date and time of day. Each colour represents a different date. Example depicting situation at 04:00 GMT Tuesday. (Times are approximate, since time zone boundaries generally do not exactly coincide with meridians.
The Geochron was the first world clock to display day and night on a world map, showing the sinh "bell curve" of light and darkness. The Geochron employs an intricate analog clockwork mechanism for its display, that shows the month, date, day of the week, hours and minutes, the areas of the world currently experiencing day and night , and the ...
Earth Clock is a computer program that will display a map of the Earth showing the zones where is day and where is night. [1] It was released by Xentax Foundation on February 7, 2004, [1] [2] and programmed by Arjan Dikhoff. Its source code can be found at SourceForge. [3]