From: Dan Martinez <dfm@...>
Date: 2012-02-17T13:05:42+09:00
Subject: [ruby-core:42707] [ruby-trunk - Bug #6042][Open] DateTime::jd off by 12 hours(?)


Issue #6042 has been reported by Dan Martinez.

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Bug #6042: DateTime::jd off by 12 hours(?)
https://bugs.ruby-lang.org/issues/6042

Author: Dan Martinez
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 
ruby -v: 1.9.2-p290


I am deeply reluctant to file a bug against something so fundamental as DateTime, and wonder whether I might have missed something, but:

When passed an integral value, DateTime::jd returns a DateTime object whose time is set to midnight GMT:

puts DateTime.jd 2455972
2012-02-14T00:00:00+00:00

The WikiPedia entry for "Julian Day" reads, in part: "Julian day is used in the Julian date (JD) system of time measurement for scientific use by the astronomy community, presenting the interval of time in days and fractions of a day since January 1, 4713 BC Greenwich noon."

It therefore seems to me that a whole number of days since that time would itself necessarily fall on Greenwich noon.

Please feel free to tell me that I'm missing something blindingly obvious.



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