Re: Julian Day Number

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Michael Covington wrote:
Todd Carnes wrote:
Well in astrophysics "Julian Day Number" and "Julian Date" have seperate and distinct meanings. I was using the term in an astrophysics context, but I guess shouldn't have assumed everyone would know what I was talking about.

An example of what I'm looking for is if I enter the date 02 Feb 1989, I want the number 2447559.5 returned. I do NOT want a conversion to the Julian calendar.

Actually "Julian Day Number" and "Julian Date" are the same thing (a number on the order of 2,400,000 for dates near the present, potentially including a fractional part for time of day) and go back to a system devised by Julius Scaliger a few centuries ago.

The "Julian Calendar" of Julius Caesar is unrelated.

Sadly, in the database world, some people use "Julian date" for any kind of day number. I would call that a "scalar date" (date expressed as a single number).

When I say Julian date, I mean just that. The date on the Julian Calendar (vice the Gregorian Calendar). That's certainly nothing like the Julian Day Number of my original question. Nor is it what you are talking about.

Having said that, I have run into something similar to what you are talking about. When I was in the military, We used to have what we called a "Julian Date" that was a different animal all together.

In the military a "Julian Date" is formed by combining the last digit of the year with the number of the day in the year. By that I mean, 31 Jan 2009 would be 9031, 01 Feb 2009 would be 9032, etc... then you'd end up at 9365 and 01 Jan 2010 would be 0001. However, the military is the *only* place I've ever seen this dating system used.

Calendars can be (and often are) quite confusing at times. :)

Todd
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