xslt 1.0 subtract date - xslt

Question

We have Sterling B2B Integrator for our EDI processing. I have a need to add the date to a file name, however, I need to assign yesterday's date and have not found a good option. I'm too new to xslt to figure it out.
It is in xlst 1.0. It looks like we have a date extension - xmlns:date="http://exslt.org/dates-and-times
I have this set up in our style sheet which works to give me the date for when it's run. Any non complex suggestions on how to get this to be yesterday's date?
<xsl:variable name="CUSTOM4">
<xsl:value-of select="date:format-date(date:date(),'yyyyMMdd')"/>
</xsl:variable>

Answer 1

I found this link to help your question.I think this is the one what you need to get privious day.
http://www.xsltfunctions.com/xsl/functx_previous-day.html
Good Luck !

Answer 2

You might have better luck computing the date using a BP then injecting it as a parameter to the XSLT
Here is a BP fragment:
<operation name="PreviousDay">
<participant name="TimestampUtilService"/>
<output message="TimestampUtilServiceArgs">
<assign to="." from="*"></assign>
<assign to="action">add</assign>
<assign to="baseTime">now</assign>
<assign to="format">yyyyMMdd</assign>
<assign to="offsetTime">-1</assign>
<assign to="scale">day</assign>
</output>
<input message="inmsg">
<assign to="." from="*"></assign>
</input>
</operation>