I've set up Xen server under Linux with several guests running, and all was well. After some time I've noticed the clock on the server drifted away, so I installed 'ntpd', and the clock was back to normal. However, my Xen guests still had the old clock. Is there a way for guests to always have the same clock value as on the server? So that each time 'ntpd' synchronizes it on the server, guests would have it changed as well.
Newer versions of Xen do not have the clock sharing feature, and the independent_wallclock setting does not exits. Your best bet is to install ntpd on all guests as well as dom0. You can try openntpd for a simple ntp daemon.