loop.xsl

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
	exclude-result-prefixes="xsl">

<xsl:template name="loop"> <!-- Loop -->
	<xsl:param name="i" />
	<xsl:param name="limit" />
	
	<xsl:call-template name="loop-item">
		<xsl:with-param name="i" select="$i"/>
		<xsl:with-param name="limit" select="$limit"/>
	</xsl:call-template>
	
	<xsl:choose>
		<xsl:when test="$i &lt; $limit">
			<xsl:call-template name="loop">
				<xsl:with-param name="i" select="$i + 1" />
				<xsl:with-param name="limit" select="$limit" />
			</xsl:call-template>
		</xsl:when>
		<xsl:when test="$i &gt; $limit">
			<xsl:call-template name="loop">
				<xsl:with-param name="i" select="$i - 1" />
				<xsl:with-param name="limit" select="$limit" />
			</xsl:call-template>
		</xsl:when>
	</xsl:choose>
</xsl:template>

<xsl:template name="loop-item"> <!-- Empty Loop Item, has to be overloaded -->
	<xsl:param name="i" />
	<xsl:param name="limit" />
</xsl:template>

</xsl:stylesheet>

page.xsl

<xsl:template match="data">
	<xsl:apply-templates select="your-ds" />
</xsl:template>

<xsl:template match="your-ds">
	<h2><xsl:value-of select="section" /></h2>
	
	<xsl:call-template name="years" />
</xsl:template>

years.xsl

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
	xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
	exclude-result-prefixes="xsl">

<xsl:import href="../utilities/loop.xsl"/>

<xsl:template name="years"> <!-- Years-wrapper for Loop -->
	<xsl:param name="from" select="$this-year" />
	<xsl:param name="to" select="'1990'" />
	
	<xsl:call-template name="loop">
		<xsl:with-param name="i" select="$from" />
		<xsl:with-param name="limit" select="$to" />
	</xsl:call-template>
</xsl:template>

<xsl:template name="years-item"> <!-- Years-Item, called by loop item -->
	<xsl:param name="i" />
	<xsl:param name="limit" />
	
	<xsl:if test="entry[substring(datum, 1, 4) = $i]">
		<h3><xsl:value-of select="$i" /></h3>
		<ul>
			<xsl:apply-templates select="entry[substring(datum, 1, 4) = $i]"/>
		</ul>
	</xsl:if>
</xsl:template>

<xsl:template name="loop-item"> <!-- Overload for Loop Item -->
	<xsl:param name="i" />
	<xsl:param name="limit" />
	
	<xsl:call-template name="years-item">
		<xsl:with-param name="i" select="$i" />
		<xsl:with-param name="limit" select="$limit" />
	</xsl:call-template>
</xsl:template>

</xsl:stylesheet>