Sunday, June 14, 2009 – Permalink –
Gregorian to/from Julian
Julian dates refer to the number of days from the first of the year and the number of days until the end of the year.
The year -45 has been called the "year of confusion," because in that year Julius Caesar inserted 90 days to bring the months of the Roman calendar back to their traditional place with respect to the seasons. This was Caesar's first step in replacing a calendar that had gone badly awry. Caesar created a solar calendar with twelve months of fixed lengths and a provision for an intercalary day to be added every fourth year. As a result, the average length of the Julian calendar year was 365.25 days.
Calendars by L. E. Doggett
From Chip Pearson's site CPearson.com:
"Many applications (especially mainframe systems) store dates in the Julian format, which is a 5-digit number, consisting of a 2-digit year and a 3-digit day-of-year number. For example, 24-August-1999 is stored as 99236, since 24-August is the 236th day of the year. Excel does not support Julian dates directly, but you can use them with only a few fairly simple formulas.
US Naval Observatory has this definition (and a calculator):
Julian dates (abbreviated JD) are simply a continuous count of days and fractions since noon Universal Time on January 1, 4713 BCE (on the Julian calendar). Almost 2.5 million days have transpired since this date.
April 29, 2004 at 6:00 AM would be 2453854.75
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<Doug Klippert@ 3:43 AM
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