XSL Example - Group by year from "date"

announcements_grouped_by_year.xsl

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output method="html" indent="yes"/>
    <xsl:key name="group-by-group" match="Row" use="@Group"/>
    <xsl:key name="group-by-year" match="Row" use="substring(@date,4,4)"/>
    <xsl:template match="/">
        <ul>
            <xsl:apply-templates select="/dsQueryResponse/Rows/Row[count(. | key('group-by-year', substring(@date,4,4))[1]) = 1]" mode="header">
                <xsl:sort select="substring(@date,4,4)"/>
            </xsl:apply-templates>
        </ul>
    </xsl:template>
    <xsl:template match="Row" mode="header">
        <li><xsl:value-of select="substring(@date,4,4)"/>
        <ul>
            <xsl:apply-templates select="key('group-by-year',substring(@date,4,4))" mode="content">
                <xsl:sort select="substring(@date,4,4)"/>
                <xsl:sort select="substring(@date,9,2)"/>
                <xsl:sort select="substring(@date,12,2)"/>
            </xsl:apply-templates>
        </ul>
        </li>
    </xsl:template>
    <xsl:template match="Row" mode="content">
        <li>
            <xsl:value-of select="@Title"/>
            <xsl:value-of select="substring(@date,4,4)"/>-<xsl:value-of select="substring(@date,9,2)"/>-<xsl:value-of select="substring(@date,12,2)"/>
        </li>
    </xsl:template>
</xsl:stylesheet>