WP 34S conversion error

[Didier Lachieze]

(12-09-2014 07:03 AM)walter b Wrote:  

(10-10-2014 07:44 PM)walter b Wrote:  I think that's the reason the light year was defined based on an average year per convention. ... Has anybody an idea, however, why they took the Julian instead of the Gregorian year? The latter would have been more consistent IMHO but I'm no astronomer.

Any astronomers out there?

d:-?

I'm not an astronomer and this may not fully answer your question but here is a hint about usage of Julian dates in astronomy:

Quote:Astronomers, unlike historians, frequently need to do arithmetic with dates. For example: a double star goes into eclipse every 1583.6 days and its last mid-eclipse was measured to be on October 17, 2003 at 21:17 UTC. When is the next? Well, you could get out your calendar and count days, but it's far easier to convert all the quantities in question to Julian day numbers and simply add or subtract. Julian days simply enumerate the days and fraction which have elapsed since the start of the Julian era, which is defined as beginning at noon on Monday, 1st January of year 4713 b.c.e. in the Julian calendar. This date is defined in terms of a cycle of years, but has the additional advantage that all known historical astronomical observations bear positive Julian day numbers, and periods can be determined and events extrapolated by simple addition and subtraction. Julian dates are a tad eccentric in starting at noon, but then so are astronomers (and systems programmers!)—when you've become accustomed to rising after the “crack of noon” and doing most of your work when the Sun is down, you appreciate recording your results in a calendar where the date doesn't change in the middle of your workday. But even the Julian day convention bears witness to the eurocentrism of 19th century astronomy—noon at Greenwich is midnight on the other side of the world. But the Julian day notation is so deeply embedded in astronomy that it is unlikely to be displaced at any time in the foreseeable future.

(Source: Julian day).

Herschel originated the use of the Julian day system in astronomy.