Вот чистое решение XSLT 1.0, которое предполагает допустимый ввод:
<xsl:template match="/">
<newdate>
<xsl:call-template name="convertdate">
<xsl:with-param name="date" select="date"/>
</xsl:call-template>
</newdate>
</xsl:template>
<xsl:template name="convertdate">
<xsl:param name="date"/>
<xsl:variable name="day">
<xsl:value-of select="number(substring-after(substring-after($date,'-'), '-'))"/>
</xsl:variable>
<xsl:variable name="suffix">
<xsl:choose>
<xsl:when test="$day = '1'">st</xsl:when>
<xsl:when test="substring($day, string-length($day), 1) = '1' and not(starts-with($day, '1'))">st</xsl:when>
<xsl:when test="substring($day, string-length($day), 1) = '2' and not(starts-with($day, '1'))">nd</xsl:when>
<xsl:when test="substring($day, string-length($day), 1) = '3' and not(starts-with($day, '1'))">rd</xsl:when>
<xsl:otherwise>th</xsl:otherwise>
</xsl:choose>
</xsl:variable>
<xsl:variable name="mo">
<xsl:value-of select="number(substring-before(substring-after($date,'-'), '-'))"/>
</xsl:variable>
<xsl:variable name="month">
<xsl:choose>
<xsl:when test="$mo = 1">Jan</xsl:when>
<xsl:when test="$mo = 2">Feb</xsl:when>
<xsl:when test="$mo = 3">Mar</xsl:when>
<xsl:when test="$mo = 4">Apr</xsl:when>
<xsl:when test="$mo = 5">May</xsl:when>
<xsl:when test="$mo = 6">Jun</xsl:when>
<xsl:when test="$mo = 7">Jul</xsl:when>
<xsl:when test="$mo = 8">Aug</xsl:when>
<xsl:when test="$mo = 9">Sept</xsl:when>
<xsl:when test="$mo = 10">Oct</xsl:when>
<xsl:when test="$mo = 11">Nov</xsl:when>
<xsl:when test="$mo = 12">Dec</xsl:when>
</xsl:choose>
</xsl:variable>
<xsl:value-of select="$day"/><xsl:value-of select="$suffix"/> <xsl:value-of select="$month"/>
</xsl:template>