RE: [xsl] XSLT 2.0/XPath 2.0 Date arithmetic

Subject: RE: [xsl] XSLT 2.0/XPath 2.0 Date arithmetic
From: "Michael Kay" <mike@xxxxxxxxxxxx>
Date: Thu, 18 May 2006 08:27:54 +0100
> Given a parameter, let's call it "today" in the form of this 
> string "20060517", how do I create a variable, let's call it 
> "tMinus1" such that it represents a day earlier than 
> "20060517", that would be "20060516". So long as "$today" 
> isn't the first day of a month, a simple subtraction and 
> followed by a type cast that I don't grasp would do the trick.
> What I'm looking for is guidance on date arithmetic.

You'd be much better off working with the xs:date type, which uses the
format 2006-05-17.

So, two functions to convert between your non-standard dates and standard
xs:date objects:

  <xs:schema target-namespace="http://my-date";>
    <xs:simpleType name="yyyymmdd-date">
      <xs:restriction base="xs:string">
        <xs:pattern value="[0-9]{4}[0-1][0-9][0-3][0-9]"/>

<xsl:function name="f:to-iso-date" as="xs:date">
  <xsl:param name="in" as="my:yyyymmdd-date"/>
  <xsl:sequence select="xs:date(replace($in, '(\d{4})(\d{2})(\d{2})',

<xsl:function name="f:to-yyyymmdd-date" as="my:yyyymmdd-date">
  <xsl:param name="in" as="xs:date"/>
  <xsl:sequence select="my:yyyymmdd-date(translate(string($in, '-', ''))"/>

   select="f:to-yyyymmdd-date(f:to-iso-date($input-date) -

If you're not schema-aware, then use xs:string in place of my:yyyymmdd-date
- all you lose is type-checking.

Michael Kay

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