XSLT - sorting by date

I'm looking at converting this XSL template from sorting a-z to date ascending and descending. There are two tags that I could utilise to sort date by:

<delivery_start_date>05-Feb-2015</delivery_start_date>

and

<machine_date>20150205</machine_date>

I had tried applying sort like this:

<xsl:sort select="@machine_date" data-type="numeric" order="ascending"/>

However that resulted in no styling being applied to the XML. The template I have is:

<?xml version="1.0" encoding="windows-1251"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://ift.tt/tCZ8VR" exclude-result-prefixes="xhtml">

  <xsl:output method="html"/>

  <!-- Assigning first-letter key to the nodes -->
  <xsl:key name="items-key" match="//*[local-name()='div' and @class='infoItem']/*[local-name()='p']/*[local-name()='a']" use="substring(., 1, 1)" />

<!--  <xsl:template match="*[local-name()='html']">-->

  <xsl:template match="*[local-name()='html']">
    <xsl:call-template name="make-indexes">
      <xsl:with-param name="nodelist" select="//*[local-name()='div' and @class='infoItem']/*[local-name()='p']/*[local-name()='a']" />
      <xsl:with-param name="key-name" select="'items-key'" />
    </xsl:call-template>
  </xsl:template>

    <!--        
        See http://ift.tt/11erA1K
        Main index template

        Properties:
        nodelist — set of nodes the index is to be based on, must equal the number of nodes in the items key of call-template
        count-columns — number of columns
        direction — way of filling columns with data (0 — vertical, 1 — horizontal)

    -->

  <xsl:template name="make-indexes">

    <xsl:param name="nodelist"/>
    <xsl:param name="key-name"/>


    <!-- Grouping using Muenchian method -->
    <xsl:variable name="blocks" select="$nodelist[generate-id(.) = generate-id(key($key-name, substring(., 1, 1)))]"/>

   <!-- Alphabetical Links -->
    <div class="alphalist">
      <ul class="inline">
        <xsl:apply-templates select="$blocks" mode="alpha-indexes">
          <xsl:with-param name="key-name" select="$key-name"/>
          <xsl:sort select="."/>
        </xsl:apply-templates>
      </ul>
    </div>

    <xsl:comment>Letter Blocks START</xsl:comment>
    <div class="alphalinks" style="float:left;">
      <xsl:for-each select="$blocks">
        <xsl:sort select="."/>

        <xsl:apply-templates select="." mode="block-indexes">
          <xsl:with-param name="key-name" select="$key-name"/>
        </xsl:apply-templates>

      </xsl:for-each>
    </div>
    <xsl:comment>Letter Blocks END</xsl:comment>

  </xsl:template>


  <!-- Alphabetical Links Template -->

  <xsl:template match="* | @*" mode="alpha-indexes">

    <xsl:param name="key-name"/>

    <xsl:variable name="letter">
      <xsl:value-of select="substring(., 1, 1)"/>
    </xsl:variable>

    <li>
      <a href="#{$letter}">
        <xsl:value-of select="$letter"/>
      </a>
    </li>
  </xsl:template>



  <!-- Block template -->

  <xsl:template match="* | @*" mode="block-indexes">
    <xsl:param name="key-name"/>
    <xsl:variable name="letter">
      <xsl:value-of select="substring(., 1, 1)"/>
    </xsl:variable>

    <a name="{$letter}" />
    <h2>
      <xsl:value-of select="$letter"/>&#160;
      <span style="font-size:small">
      <a href="#">top</a>
      </span>
    </h2>
    <ul>
      <xsl:comment>Links for letter <xsl:value-of select="$letter"/> START</xsl:comment>
      <xsl:apply-templates select="key($key-name, substring(., 1, 1))" mode="item-indexes">
        <xsl:sort select="."/>
      </xsl:apply-templates>
      <xsl:comment>Links for letter <xsl:value-of select="$letter"/> END</xsl:comment>
    </ul>

  </xsl:template>

    <!-- Block contents template -->

  <xsl:template match="* | @*" mode="item-indexes">

    <li>
            <!--<xsl:copy />-->
      <xsl:element name="a">
        <xsl:attribute name="href">
          <xsl:value-of select="@href"/>
        </xsl:attribute>
        <xsl:value-of select="."/>
      </xsl:element>

            <!--<xsl:value-of select="."/>-->
    </li>

  </xsl:template>

</xsl:stylesheet>

What would be the solution for me to sort by date?