I reply myself for completeness...
On Mon, Aug 31, 2015 at 2:46 PM, [IDIS Technical Secretariat] Ricardo
Rodríguez <ricardo.rodriguez(a)idisantiago.es> wrote:
  Hi!
 The server where our XWiki 7.1.2. installation is running is in CEST
 timezone. We do need to read dates in GMT timezone and find this...
 How can I format a date in a different time zone in Velocity Template
 using DateTool?
http://stackoverflow.com/questions/21691445/how-can-i-format-a-date-in-a-di…
 I'm not able to get this running. Please, could somebody provide an
 example of using or any other way to transform the date to GMT?
 
In the same XWiki page I can use Groovy to instantiate TimeZone and get a
TimeZone object with the desired value...
{{groovy}}
xcontext.put("sTimezone", java.util.TimeZone.getTimeZone("GMT"))
{{/groovy}}
Also, complete the Velocity script to add a variable to store my locale...
{{velocity}}
#set($sLocale = $datetool.getLocale())
...
{{/velocity}}
Then, I call it from Velocity...
{{velocity}}
...
#set($date = $datetool.format('d MMM yyyy hh:mm:ss z', $rcDoc.date,
$sLocale, $xcontext.sTimezone))
...
{{/velocity}}
I'll add this comments to the concerned Timeline Extension page in 
xwiki.org.
Here there is an example running in our own server...
http://portal.idisantiago.es/xwiki/bin/view/Home/Timeline
Any comment will be extremely welcome! Thanks!
Cheers,
Ricardo
  Thank you for your help!
 Ricardo
 --
 Ricardo Rodríguez
 Research Management and Promotion Technician
 Technical Secretariat
 Health Research Institute of Santiago de Compostela (IDIS)
 
http://www.idisantiago.es
 
--
Ricardo Rodríguez
Research Management and Promotion Technician
Technical Secretariat
Health Research Institute of Santiago de Compostela (IDIS)
http://www.idisantiago.es