Please describe the problem:
The number reurned is one less than the actual ISO8601 numbered week

Steps to reproduce:
1. create basic xsl stylesheet with these lines in the stylesheet element
    xmlns:date="http://exslt.org/dates-and-times"
        extension-element-prefixes="date"
2. create xsl:template for "/" element
3. add <xsl:value-of select="date:week-in-year('2006-01-16'))" />
4. close xsl:template
5. attempt to parse any well-formed xml-document
6. This occured while using PHP 5 and the XSL extension (core)

Actual results:
The week is printed as 2 instead of 3

Expected results:
The week should be printed as 3

Does this happen every time?
Yes

Other information:
Should be simple to correct