GNU bug report logs - #21903
date->string duff ISO 8601 negative years

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Package: guile;

Reported by: Zefram <zefram <at> fysh.org>

Date: Fri, 13 Nov 2015 14:03:02 UTC

Severity: normal

Done: Mark H Weaver <mhw <at> netris.org>

Bug is archived. No further changes may be made.

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From: Zefram <zefram <at> fysh.org>
To: 21903 <at> debbugs.gnu.org
Subject: bug#21903: date->string duff ISO 8601 negative years
Date: Fri, 13 Nov 2015 14:01:57 +0000

The date->string function from (srfi srfi-19), used on ISO 8601 formats
"~1", "~4" and "~5", for years preceding AD 1, has an off-by-one error:

scheme@(guile-user)> (use-modules (srfi srfi-19))
scheme@(guile-user)> (date->string (julian-day->date 0 0) "~4")
$1 = "-4714-11-24T12:00:00Z"

The date in question, the JD epoch, is 24 November 4714 BC (in the
proleptic Gregorian calendar).  In ISO 8601 format, that year is properly
represented as "-4713", not "-4714", because ISO 8601 uses the AD era
exclusively.  4714 BC = AD -4713.

-zefram
This bug report was last modified 6 years and 211 days ago.

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