xsl:variable with a xsl:call-template

When i define a xsl:variable using a xsl:call-template, is the call-template
applied every time
i use this xsl:variable or just ones when i define the xsl:variable?

ex.

<xsl:variable name="unique-dates">
<xsl:call-template name="template_unique-dates">
<xsl:with-param name="doc" select="document($xmldata)"/>
</xsl:call-template>
</xsl:variable>
...
<xsl:template match="root">
run 1
<xsl:value-of select="$unique-dates"></xsl:value-of>
run 2 <!-- do i call template_unique-dates again or not ????? -->
<xsl:value-of select="$unique-dates"></xsl:value-of>
</xsl:template>
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