Conversions for PeopleSoft input

Hi,
	Can someone tell me why this does not work?  I am trying to convert the
date from a Siebel format to a PeopleSoft format.

Input data is date in format:  MM/DD/YYYY HH:MM:SS 
i.e: 02/06/2003 00:00:00

I need the output as YYYY-MM-DD

XSLT that I am trying to use to transform this is:

<QUOTE_DUE_DATE><xsl:value-of select="concat(substring(EndDate, 7, 4), '-',
substring(EndDate, 1, 2), '-', substring(EndDate, 4, 2))"/>
				</QUOTE_DUE_DATE>		


I am very new to XSLT (only know what we were taught as part of a PeopleSoft
class) so please explain in simple terms.
Thanks,
Bridget

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