ntp is the time daemon. Servers don't like not to be in sync. Configure it with yast, it's very simple to use any ntp server yast is proposing. Don't forget to activate the ntp service.
ovh / Kimsufi
YaST warned me that the config file was hand modifed. In fact my provider (ovh) already setup it's own ntp server (ntp.ovh.com) in the file.