Re: date formatting function

I guess my question, given what I want to do, is how should I construct the function; as a single function -- let's call it bib:format-month-day -- that when called takes any YYYY/YYYY-MM/YYYY-MM-DD string and returns the formatted date (with parameter for whether months are rendered as full or abbreviated)?

That's where I was headed. But if that's sensible, I'm not sure how to actually code it; .e.g. what goes inside the "when" below:

     <xsl:when test="$date castable as xs:gYearMonth">
       ...
     </xsl:when>

Or, more specifically, how do I take the statement "xs:date(concat($date, '-01'))" and then use format-date on it?

  <xsl:function name="mods:format-month-day">
    <xsl:param name="date"/>
    <xsl:variable name="date" select="$date" />
    <xsl:choose>
      <xsl:when test="$date castable as xs:gYearMonth">
        <xsl:variable name="month-day"
          select="xs:date(concat($date, '-01'))"/>
        <xsl:value-of
          select="format-date($month-day,'[MNn,*-3].')"/>
      </xsl:when>
      <xsl:when test="$date castable as xs:date">
        <xsl:value-of select="format-date($date,'[MNn,*-3]. [D]')"/>
      </xsl:when>
    </xsl:choose>
  </xsl:function>

  <xsl:template match="date">
    <h2>Dates:</h2>
    <p class="date">
      <xsl:value-of select="mods:format-month-day(.)"/>
    </p>
   </xsl:template>