If you want to convert decimal values into hours and minutes, and you are stuck with XSLT, use this.
<xsl:stylesheet version="3.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text"/>
<xsl:variable name="decimal_hours" select="3.14"/>
<xsl:template match="/">
<xsl:value-of select="concat(
format-number(floor($decimal_hours ), '00:'),
format-number(floor($decimal_hours * 60 mod 60), '00:'),
format-number(floor($decimal_hours * 360 mod 360), '00'))"/>
</xsl:template>
</xsl:stylesheet>