Finally I figured out where to set the time sync option in Suse 9. Unlike RedHat Suse doesn't ask you during installation whether and which public time server to use:
Control Center -> YAST2 modules -> Network Service -> NTP client -> Authenticate as administrator -> Delete the CMOS entry -> Add
Type the address of a public time server. I used this time fartein.ifi.uio.no, but there is a long list with server to choose from at http://support.ntp.org/bin/view/Servers/WebHome.