Eucalyptus Versions: All
libvirt provides a method whereby guest clock synchronisation can be configured in the domain XML, which is the definiton for a guest machine.
By default the guest is configured to synchronise the guest clock to the host phyical machines configured timezone, using the "localtime" value. This is not always optimal and can be changed.
Modifying the Eucalyptus libvirt template
Eucalyptus templates the libvirt machine definition for each instance via the libvirt.xsl file in /etc/eucalyptus/ on each node controller. Open this file and modify the following line:
<clock offset="localtime" />
Change the value accordingly. You will need to make this change on all of your node controllers if you wish for it to persistent and be the same for all instances.