adjust-dateTime-to-timezone function in xsl stylesheet

I  tried
<xsl:value-of
select="adjust-dateTime-to-timezone($adjDate,xs:dayTimeDuration('P0DT4H'))"/>

but its not working for me, I get no result.

my adjDate variable is in the format
2014-01-25T00:00:00

and was declared here:
<xsl:variable
name="adjDate" as="xs:dateTime"
select="concat(substring($oldDate,1,4),'-',substring($oldDate,5,2),'-',substring($oldDate,7,2),'T',substring($oldDate,9,2),':',substring($oldDate,11,2),':',substring($ol
dDate,13,2))"/>

Do I have the
incorrect syntax somewhere?

Please help !

thank you!