Timezone and date +%s command

Shell Programming and Scripting
1

DST started on Oct 20th in Brazil.
If I run the below command in that time zone,
date +%s -d "10/20/2013" it throws an error message "Invalid date" . But it works fine for other dates including 19th and 21st Oct.
Any idea ? Is there any unix patch ?

2

Which OS ?
Post result of following

$ date --version

$ uname -a
3 
# uname -a
Linux auto172a20-116-91 2.6.18-238.1.1.el5 #1 SMP Tue Jan 4 13:32:19 EST 2011 x86_64 x86_64 x86_64 GNU/Linux

# date --version
date (GNU coreutils) 5.97
Copyright (C) 2006 Free Software Foundation, Inc.
This is free software.  You may redistribute copies of it under the terms of
the GNU General Public License <http://www.gnu.org/licenses/gpl.html>.
There is NO WARRANTY, to the extent permitted by law.

Written by David MacKenzie.