Julian dating system

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For further information on calendars, see Richards, E.

We refer to a yyddd date format (yy = year, ddd=day) as a 'Julian Date' - this is the common term for such a date in mainframe and other circles.

Most astronomy texts explain that it is based on the number of days that have elapsed since noon universal time (UT), 1 January 4713 BCE (before current era, or B. If you think that "Julian" refers to the Julian calendar, named after the Roman emperor Julius Caesar, you are both right and wrong. This system was named after Julius Caesar, but not the one who ruled Rome and was assassinated by Brutus and others.

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The ancients knew the length of the year fairly accurately, as well as the length of the lunar cycle.For example, for England and its colonies, the change did not occur until September 1752. The API returns data in Java Script Object Notation (JSON) format for users who wish to manipulate data into a customized format. (The Unix cal command for systems manufactured in the U. reflects the 1752 changeover.) For a list of when certain countries switched to the Gregorian calendar, see Claus Tøndering's Calendar FAQ. For more information on the API, please see the documentation page. Julian dates are widely used as time variables within astronomical software.Typically, a 64-bit floating point (double precision) variable can represent an epoch expressed as a Julian date to about 1 millisecond precision.

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