Timezone error in calculating dates of equinoxes and solstices

Timezone error in calculating dates of equinoxes and solstices

[Larry Denenberg]

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In GNU Emacs 21.1.2 (sparc-sun-solaris2.5, X toolkit)
 of 2002-05-23 on stay.intouchsys.com
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: nil
  locale-coding-system: nil
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

In timezone US/Eastern, emacs reports the wrong date for this year's
autumnal equinox.  It should be 12:55 AM EDT September 23 but is
reported as 12:55 AM EDT September 22.

    (setq displayed-month 9)
    9
    (setq displayed-year 2002)
    2002
    (solar-equinoxes-solstices)
    (((9 22 2002) "Autumnal Equinox 12:55am (EDT)"))

When I run emacs with TZ=US/Central, the last command correctly returns
    (((9 22 2002) "Autumnal Equinox 11:55pm (CDT)"))

I believe that the bug is in function solar-equinoxes-solstices, which
doesn't correctly convert the result of solar-equinoxes/solstices to
daylight time.

/Larry Denenberg
larry@denenberg.com
http://larry.denenberg.com/