I didn't try to diagnose the problem. I just switched. I do not claim that OpenNTPD has a bug. Maybe it has requirements on the quality of the local clock that

I didn't try to diagnose the problem. I just switched. I do not claim that OpenNTPD has a bug. Maybe it has requirements on the quality of the local clock that the virtual machine didn't meet. Maybe it has requirements on the remote time sources or the network that the setup didn't meet. What I do know is that over the years I've deployed ntp-over-the-Internet in a dozen or two different setups (including some user-mode-Linux ones with really poor local clocks), and ntp.org's ntpd has always managed to sync the clock. The one time I gave OpenNTPD a go it didn't. Looking at the log, I was running it for several months. After a while I got tired of fixing it manually when the clock was a few seconds out.