... stuff ...
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
	xmlns:exsl="http://exslt.org/common"
	xmlns:ms="urn:schemas-microsoft-com:xslt" 
    extension-element-prefixes="exsl ms">
... stuff ...
<xsl:template name="month-name">
<!--returns the name of the month from its number-->
  <xsl:param name="this-month" select="number(0)" />
  <xsl:variable name="months">
    <month short="Jan">January</month>
    <month short="Feb">February</month>
    <month short="Mar">March</month>
    <month short="Apr">April</month>
    <month short="May">May</month>
    <month short="Jun">June</month>
    <month short="Jul">July</month>
    <month short="Aug">August</month>
    <month short="Sep">September</month>
    <month short="Oct">October</month>
    <month short="Nov">November</month>
    <month short="Dec">December</month>
  </xsl:variable>
  <xsl:choose>
    <xsl:when test="function-available('exsl:node-set')">
      <xsl:value-of select="exsl:node-set($months)/month[$this-month]/@short"/>
    </xsl:when>
    <xsl:when test="function-available('ms:node-set')">
      <xsl:value-of select="ms:node-set($months)/month[$this-month]/@short"/>
    </xsl:when>
    <xsl:otherwise>
      <xsl:value-of select="concat($this-month, ' /')"/>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</xsl:stylesheet>