I am working on some xmltv files. An xmltv file (as described in
www.xmltv.org) is a XML file containing TV programme information.
The programme listings look like this:
 <tv>
<programme channel="tpg.aljazeera" start="20080430040000 +0100"
stop="20080430043000 +0100"> [...]

As you can see, the programme contains one attribute: start which is a
date in the format YYYYMMDDHHMMSS [+-]XXXX where XXXX is the timezone.

I have written an XSLT template (I've attached the code below) that
converts that date to UTC as the xmltv file will contain various
programme, all in different timezone depending on the source.

What I'm trying to achieve, is sort the XML file based on the start
attribute, but *after* it has been converted to UTC

Can't you just preprocess the data in order to add an attribute @ts
holding a good old UNIX timestamp, and another attribute, if needed,
holding a value for display?

The way I would convert my date, with my template/function is:
	<xsl:variable name="utcstart">
		<xsl:call-template name="UTCDate">
			<xsl:with-param name="DateTime" select="@start"/>
		</xsl:call-template>
	</xsl:variable>

Is this something that would be possible with XSLT?
if not, could you suggest a work around ?

I think this could work, but I'd embed the XSLT part in a host language
like Perl, PHP, or Java, and then use mktime and strftime (or their Java
equivalents) to handle dates and times.

-- My UTC convert template: Unfortunately, I want this to run in my
web browser, and I haven't found one compatible with XSLT 2.0, so I
had to do everything by hand.

I think this is, indeed, unfortunate. Are you sure you can't do part of
the work on the server side? There, you may find better tools for the
job. XSLT, even 1.0, certainly is great, but it's not the only tool in
the box. In the web browser, however, you can't escape to host languages
as you can on the server side. So there's a lot of things that are very
hard to tackle in the browser.

And I think we'll have to wait for a couple of years to see widespread
support for 2.0 in web browsers.

Even on the server side, if you use Perl or PHP or Python, you'll very
likely use LibXSLT, which means XSLT 1.0.

I haven't checked this XSLT - but it's so much easier in other
languages, which have all the functionality you need to handle dates.

http://de3.php.net/manual/en/xsltprocessor.registerphpfunctions.php
http://search.cpan.org/dist/XML-LibXSLT/LibXSLT.pm - register_function