In the fifth century CE the scholar Zu Chongzi created the first calendar which took precession into account, and the This problem is called Precession and was recorded by Chinese historians in the fourth and fifth centuries CE.
Over such a long period of observation, Chinese astronomers became aware that theirĬalendar was not accurate, and by the second century CE it was recognised that the calendar became unreliable every 300 years. However, traditional Chinese records suggest the origin of a calendar of 366 days depending on the movements of the Sun and the Moon as early as 3,000 BCE. They show a 12 month year with the occasional occurrence of a 13th month. The earliest archaeological evidence of Chinese calendars appears about 2,000 BCE. Their base 60 fraction system which we still use today (degrees / hours, minutes and seconds) was much easier to calculate with than the fractions used in Egypt or Greece,Īnd remained the main calculation tool for astronomers until after the 16th century, when decimal notation began to take over. The Assyrian winged man-headed bull had the strength of a bull, the swiftness of a bird and human intelligence.įrom about 700 BCE the Babylonians began to develop a mathematical theory of astronomy, but the equally divided 12-constellation zodiac appears later about 500 BCE to correspond to their year of 12 months of 30 days each. NOAA.The constellation Taurus, the bull, a symbol of strength and fertility, figures prominently in the mythology of nearly all early civilizations, from Babylon and India to northern Europe. Look up UTC offsets for time zones References and Additional Reading on Sunrise Sunset Timesĭefinitions for sunrise, sunset, transit, civil dusk and dawn and other astronomical definitions. There are several resources to look up UTC offsets:
To calculate sunrise and sunset times for Portland, OR you'll need to set the time zone to Online reference to look up latitude 45° 31' north and longitude 122° 41' west. 45.534251,-122.717285 will display in the search box and can be seen when you roll over the marker.Right click on the Google map and choose "What's Here?".Google Maps to find your location, for example, Portland, Oregon. latitude 45.52° north and longitude -122.68° eastįind Coordinates for a Geographical Location.latitude 45.52° north and longitude 122.68° west or.latitude 45° 31' north and longitude 122° 41' west or.Likewise you can find and enter longitude position in terms of east and westįor example, coordinates for Portland, Oregon US can be expressed and entered as any of the following: A negative value is negative north or positive south. You can find and enter latitude position in terms of north and south Or use decimal degrees such as 42.35° north, 71.08° west (-71.08 east) and leave the minutes field blank.Įntering coordinates of longitude and latitudeĮnter degrees and minutes or degrees only, with positive or negative decimal numbers. Using Boston, MA US for example, enter degrees and minutes as 42° 21' north, 71° 5' west, This sunrise-sunset calculator finds the times for sunrise, sunset, transit (zenith), dawn and dusk based on latitude and longitude. Enter the latitude and longitude for the location of interest, along with the corresponding time zone for that location.