bug#23942: 24.4; Calc; calc-unix-time returns incorrect date

[Vladimir Grul]

Entering the following number and operation into calc window

 1468144800

 `t U'

results in

 <10:00am Mon Jul 11, 2016>

while I think the correct result should be <10:00am Mon Jul 10, 2016>







In GNU Emacs 24.4.1 (x86_64-pc-linux-gnu, GTK+ Version 3.14.5)
 of 2015-03-07 on trouble, modified by Debian
Windowing system distributor `The X.Org Foundation', version 11.0.11604000
System Description:     Debian GNU/Linux 8.5 (jessie)

Configured using:
 `configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/lib
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.4/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.4/site-lisp:/usr/share/emacs/site-lisp
 --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib
 --libexecdir=/usr/lib --localstatedir=/var/lib
 --infodir=/usr/share/info --mandir=/usr/share/man --with-pop=yes
 
--enable-locallisppath=/etc/emacs24:/etc/emacs:/usr/local/share/emacs/24.4/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/24.4/site-lisp:/usr/share/emacs/site-lisp
 --with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars
 'CFLAGS=-g -O2 -fstack-protector-strong -Wformat
 -Werror=format-security -Wall' CPPFLAGS=-D_FORTIFY_SOURCE=2
 LDFLAGS=-Wl,-z,relro'

Important settings:
  value of $LANG: cs_CZ.UTF-8
  locale-coding-system: utf-8-unix

Major mode: C++/l

Minor modes in effect:
  show-paren-mode: t
  icomplete-mode: t
  desktop-save-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Recent input:
M-x c a l c <return> <help-echo> <down-mouse-2> <drag-mouse-2> 
<help-echo> <help-echo> <help-echo> t U q M-x r e p 
o r t e m <tab> <backspace> <backspace> - e <tab> 
<return>

Recent messages:
Loading gnus...done
Loading icomplete...done
Loading paren...done
communicator.cpp has auto save data; consider M-x recover-this-file
Wrote /home/vgrul/.emacs.d/.emacs.desktop.lock
Desktop: 2 frames, 16 buffers restored.
For information about GNU Emacs and the GNU system, type C-h C-a.
Loading 
/home/vgrul/.emacs.d/session.10656e7069000146134727500000020570025...done
Restored session data
Welcome to the GNU Emacs Calculator!  Press `?' or `h' for help, `q' to quit

Load-path shadows:
/usr/share/emacs/24.4/site-lisp/debian-startup hides 
/usr/share/emacs/site-lisp/debian-startup
/usr/share/emacs24/site-lisp/cmake-data/cmake-mode hides 
/usr/share/emacs/site-lisp/cmake-mode
/usr/share/emacs24/site-lisp/dictionaries-common/flyspell hides 
/usr/share/emacs/24.4/lisp/textmodes/flyspell
/usr/share/emacs24/site-lisp/dictionaries-common/ispell hides 
/usr/share/emacs/24.4/lisp/textmodes/ispell
/usr/share/emacs/site-lisp/rst hides /usr/share/emacs/24.4/lisp/textmodes/rst

Features:
(shadow sort mail-extr emacsbug message rfc822 mml mml-sec mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums calccomp calc-arith calc-misc
cal-dst calc-alg calc-forms calc-aent calc-yank calc-ext calc-menu calc
calc-loaddefs calc-macs mule-util info org-element org-rmail org-mhe
org-irc org-info org-gnus org-docview doc-view image-mode dired
org-bibtex bibtex org-bbdb org-w3m org advice org-macro org-footnote
org-pcomplete pcomplete org-list org-faces org-entities noutline outline
easy-mmode org-version ob-emacs-lisp ob ob-tangle ob-ref ob-lob ob-table
ob-exp org-src ob-keys ob-comint comint ansi-color ring ob-core ob-eval
org-compat org-macs org-loaddefs format-spec find-func cal-menu calendar
cal-loaddefs cc-langs cc-mode cc-fonts easymenu cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs saveplace jka-compr
paren icomplete gnus gnus-ems nnheader gnus-util mail-utils mm-util
help-fns mail-prsvr wid-edit desktop frameset cl-loaddefs cl-lib
cus-start cus-load time-date tooltip electric uniquify ediff-hook
vc-hooks lisp-float-type mwheel x-win x-dnd tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment lisp-mode prog-mode register
page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core frame cham georgian utf-8-lang
misc-lang vietnamese tibetan thai tai-viet lao korean japanese hebrew
greek romanian slovak czech european ethiopic indian cyrillic chinese
case-table epa-hook jka-cmpr-hook help simple abbrev minibuffer nadvice
loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote make-network-process dbusbind
gfilenotify dynamic-setting system-font-setting font-render-setting
move-toolbar gtk x-toolkit x multi-tty emacs)

Memory information:
((conses 16 243007 6271)
 (symbols 48 34170 0)
 (miscs 40 387 270)
 (strings 32 57386 6598)
 (string-bytes 1 1730006)
 (vectors 16 23117)
 (vector-slots 8 547291 6486)
 (floats 8 145 399)
 (intervals 56 1069 0)
 (buffers 960 29)
 (heap 1024 34901 1188))