Richards in his book Mapping Time provided a diagram in which 12 a. Many U. The NIST website states that "12 a. The Associated Press Stylebook specifies that midnight "is part of the day that is ending, not the one that is beginning. The Canadian Press Stylebook  says, "write noon or midnight , not 12 noon or 12 midnight. Britain's National Physical Laboratory "FAQ-Time" web page  states "In cases where the context cannot be relied upon to place a particular event, the pair of days straddling midnight can be quoted"; also "the terms 12 a.
Likewise, some U. For an example of the latter method, "midnight" is replaced with " p. That has become common in the United States in legal contracts and for airplane , bus , or train schedules, though some schedules use other conventions. From Wikipedia, the free encyclopedia. Timekeeping system. Main article: Date and time representation by country. For the o'clock watch, see O bag. Retrieved 20 November To designate noon, either the word noon or or 12 M should be used.
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To designate midnight without causing ambiguity, the two dates between which it falls should be given unless the hour notation is used. Thus, midnight may be written: May 15—16 or May 15 or May National Institute of Standards and Technology. Retrieved 30 September Archived from the original on 4 July Retrieved 28 November Archived from the original on 13 October Retrieved 12 November Bleeping Computer.
Retrieved 26 October Boston: Houghton Mifflin, Retrieved 22 April January Retrieved 24 May University of Chicago Press. Although noon can be expressed as m. Past history deep time Present Future Futures studies Far future in religion Far future in science fiction and popular culture Timeline of the far future Eternity Eternity of the world. Horology History of timekeeping devices Main types astrarium atomic quantum hourglass marine sundial sundial markup schema watch mechanical stopwatch water-based Cuckoo clock Digital clock Grandfather clock.
Chronology History. Religion Mythology. Geological time age chron eon epoch era period Geochronology Geological history of Earth. Chronological dating Chronobiology Circadian rhythms Dating methodologies in archaeology Time geography. Time measurement and standards. Just the celestial sphere plus the ecliptic, with solstices and equinoxes marked. Drawn for northern latitudes, these are the paths the sun takes across the sky on the equinoxes and solstices. Can you see that the summer path is longer and therefore that the summer sun stays in the sky longer?
This figure illustrates that, depending on your latitude, some stars will be "circumpolar" and will never set. Examples relating observer's coordinates altitude with celestial coordinates declination for various latitudes on earth. We consider only maximum altitudes, i.
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The Macmillan Co. Note that the numbering of the seasons should be reversed if we align with a northern hemisphere bias. These two figures are supposed to illustrate the same thing: the constant Conceptual danger: these are perspective-foreshortened drawings; the actual orbit of the earth is a near-perfect circle; its distance from the sun varies by a very tiny amount 1.
Also, the numbers 2 and 4 should be swapped on the cherries in the barrel for northern hemisphere observers but perfectly correct if you view the solar system so that south is up [Thanks for pointing that out, James King]. The north pole leans toward the constellation Gemini.
Table of Sun's path along the ecliptic: Approx. It's a great summary figure after you have understood moon phases and timing. The view is from the north, looking down for the bottom half of the figure, but the view is from earth for the top row of moons. Diagram is not to scale. Moon phase information. Can you see how this tabulated information comes from the figure above? For historical reasons, the meridian passing the old Royal Astronomical Observatory in Greenwich, England, is the one chosen as zero longitude.
Located at the eastern edge of London, the British capital, the observatory is now a public museum and a brass band stretching across its yard marks the "prime meridian. A lines of longitude is also called a meridian , derived from the Latin, from meri , a variation of "medius" which denotes "middle", and diem , meaning "day. All points on the same line of longitude experienced noon and any other hour at the same time and were therefore said to be on the same "meridian line", which became "meridian" for short.
At 12 noon local time the Sun passes to the south and is furthest from the horizon northern hemisphere. Somewhere around 6 am it rises, and around 6 pm it sets. Local time is what you and I use to regulate our lives locally, our work times, meals and sleep-times.
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But suppose we wanted to time an astronomical event--e. For that we need a single agreed-on clock, marking time world-wide, not tied to our locality. That is universal time UT , which can be defined with some slight imprecision, no concern here as the local time in Greenwich, England, at the zero meridian. As the Earth rotates around its axis, at any moment one line of longitude--" the noon meridian "--faces the Sun, and at that moment, it will be noon everywhere on it.
After 24 hours the Earth has undergone a full rotation with respect to the Sun, and the same meridian again faces noon. In the middle of the 19th century, each community across the US defined in this manner its own local time, by which the Sun, on the average, reached the farthest point from the horizon for that day at 12 oclock.
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However, travelers crossing the US by train had to re-adjust their watches at every city, and long distance telegraph operators had to coordinate their times. The continental US has 4 main time zones--eastern, central, mountain and western, plus several more for Alaska, the Aleut islands and Hawaii.
Canadian provinces east of Maine observe Atlantic time; you may find those zones outlined in your telephone book, on the map giving area codes. Other countries of the world have their own time zones; only Saudi Arabia uses local times, because of religious considerations. In addition, the clock is generally shifted one hour forward between April and October.
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This " daylight saving time " allows people to take advantage of earlier sunrises, without shifting their working hours. By rising earlier and retiring sooner, you make better use of the sunlight of the early morning, and you can enjoy sunlight one hour longer in late afternoon. Fifteen degrees to the west the time is 11 a. Keeping this up, degrees away one should reach midnight, and still further west, it is the previous day.