Saxon

refering to documentation https://www.saxonica.com/html/documentation11/functions/fn/format-dateTime.html

Saxon PE and EE support https://www.saxonica.com/html/documentation11/functions/saxon/parse-dateTime.html so you would need to use e.g. saxon:parse-dateTime (and PE or EE) instead of parse-dateTime in your code. As the error message says, there is no XPath 2 or 3 function named parse-dateTime.

Ah, do you mean doing something like this:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns="http://www.w3.org/2005/xpath-functions"
  xmlns:func="http://ingka.ikea.com/"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns:int="http://ikea.com/FUI/stockreport"
   xmlns:date="http://www.w3.org/2005/xpath-functions"
   xmlns:saxon="http://saxon.sf.net/"
    version="3.0">

  <xsl:output method="text" indent="yes" omit-xml-declaration="yes" />
  <xsl:strip-space elements="*"/>    

    <xsl:param name="MessageReference" />    

	<xsl:template match="/">
		<xsl:variable name="transformed-xml">      
		<xsl:call-template name="body" />
		<xsl:copy-of select="/map"/>
		</xsl:variable>
		<!-- Added replace startment to print n/a as is, issue https://saxonica.plan.io/issues/5225-->
		<xsl:value-of select="xml-to-json($transformed-xml, map { 'indent' : true() })"/> 
	</xsl:template>

  
	<xsl:template name="body" >
		<map>
			<map key="MsgHeader">
				<xsl:call-template name="MsgHeader"/>
			</map> 
		</map>
	</xsl:template>    
  
  
	<xsl:template name="MsgHeader" >
		<string key="MsgNames"><xsl:value-of select="saxon:parse-dateTime('05/30/2018 09:00:00','MM/dd/yyyy HH:MMMX')"/></string> 
		<string key="MsgVersNo">1.0</string>
		<string key="MsgDateTime"><xsl:value-of select="format-dateTime(current-dateTime(),'[Y0001]-[M01]-[D01]T[H01]:[m01]:[s01].[f001][Z00:00]')"/></string>
	</xsl:template>    
    
</xsl:stylesheet>

its throwing back similar error *Stylesheet compilation failed with 1 error(s): Error 1 at line 36:0 : Cannot find a 2-argument function named Q{http://saxon.sf.net/}parse-dateTime(). External function calls have been disabled *

but I think it could be because I am using Saxon HE

Do you think this function would be available in Saxon HE anytime?

It's our general policy that Saxon extensions to the W3C specifications require Saxon-PE or higher.

Okay! Thankyou :)