(article-make-date-line "Sat Jan 1 00:00:00 2000 -0400" 'local)
=> "Date: Fri Dec 31 23:00:00 1999 --400"

(article-make-date-line "Sat Jan 1 00:00:00 2000 UT" 'ut)
=> "Date: Fri Dec 31 23:00:00 1999 UT"

This only happens in daylight saving area. The attached patch fix the
bug.

Shenghuo

1999-09-10  Shenghuo ZHU  <zsh@cs.rochester.edu>

	* gnus-art.el (article-make-date-line): Fix time-zone bug.