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zic: move Big Bang to - 2**59

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This should help forestall flame wars among competing camps of physicists.
(Thanks to James Cloos.)
* NEWS, zic.8 (NOTES): Document this.
* zic.c (BIG_BANG): Use - 2**59 rather than a more-precise estimate.
This commit is contained in:
Paul Eggert
2014-05-26 17:21:38 -07:00
parent 0880e2fe56
commit 1421881858
3 changed files with 14 additions and 12 deletions
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2
NEWS
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@@ -9,7 +9,7 @@ Unreleased, experimental changes
This works around GNOME bug 730332
<https://bugzilla.gnome.org/show_bug.cgi?id=730332>.
(Thanks to Leonardo Chiquitto for reporting the bug, and to
Arthur David Olson for suggesting an improvement to the fix.)
Arthur David Olson and James Cloos for suggesting improvements to the fix.)
Release 2014c - 2014-05-13 07:44:13 -0700

4
zic.8
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@@ -520,10 +520,10 @@ To get separate transitions
use multiple zone continuation lines
specifying transition instants using universal time.
.PP
Time stamps before the Big Bang are silently omitted from the output.
Time stamps well before the Big Bang are silently omitted from the output.
This works around bugs in software that mishandles large negative time
stamps. Call it sour grapes, but pre-Big-Bang time stamps are
physically suspect anyway. The estimated time of the Big Bang is
physically suspect anyway. The pre-Big-Bang cutoff time is
approximate and may change in future versions.
.SH FILE
/usr/local/etc/zoneinfo standard directory used for created files

20
zic.c
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@@ -724,29 +724,31 @@ static const zic_t min_time = (zic_t) -1 << (TIME_T_BITS_IN_FILE - 1);
static const zic_t max_time = -1 - ((zic_t) -1 << (TIME_T_BITS_IN_FILE - 1));
/* Estimated time of the Big Bang, in seconds since the POSIX epoch.
rounded downward to the negation of a power of two that is
comfortably outside the error bounds.
zic does not output time stamps before this, partly because they
are physically suspect, and partly because GNOME mishandles them; see
GNOME bug 730332 <https://bugzilla.gnome.org/show_bug.cgi?id=730332>.
The following estimate for the Big Bang time is taken from:
For the time of the Big Bang, see:
Ade PAR, Aghanim N, Armitage-Caplan C et al. Planck 2013 results.
I. Overview of products and scientific results.
arXiv:1303.5062 2013-03-20 20:10:01 UTC
<http://arxiv.org/pdf/1303.5062v1> [PDF]
Page 36, Table 9, row Age/Gyr, column Planck+WP+highL+BAO best fit,
gives the value 13.7965. Multiplying this by 1000000000 and then
by 31557600 (the number of seconds in an astronomical year), yields
435384428400000000. This estimate intentionally ignores the
difference between the POSIX epoch and the paper's publication
date, as being beneath the paper's precision.
Page 36, Table 9, row Age/Gyr, column Planck+WP+highL+BAO 68% limits
gives the value 13.798 plus-or-minus 0.037 billion years.
Multiplying this by 1000000000 and then by 31557600 (the number of
seconds in an astronomical year) gives a value that is comfortably
less than 2**59, so BIG_BANG is - 2**59.
This estimate is approximate, and may change in future versions.
BIG_BANG is approximate, and may change in future versions.
Please do not rely on its exact value. */
#ifndef BIG_BANG
#define BIG_BANG (-435384428400000000LL)
#define BIG_BANG (- (1LL << 59))
#endif
static const zic_t big_bang_time = BIG_BANG;