If a kernel will actually work on your machine, then booting it from the MacOS will get you all the way through the boot process until it has to change the root device. So if you are interested in running NetBSD on your machine for the first time, this option is a good one to try. If you are connected to the Internet, the best thing you can do is to run xntpd. A more permanent solution which doesn't require a network connection doesn't exist at the moment. Basically, a kernel task which reads the PRAM clock every so often and that sets the Real Time Clock with this value would have to be created.
Most people just live with the problem or reboot once in a while.
If you are using Booter 1.8 or later, you must be running System 7 or later system software. System 6.x.x no longer works. The problem appears to be in the booter, but no one really seems to care. In addition, many extensions distributed with later versions of MacOS may cause problems. It' generally a good idea to boot with extensions off if at all possible.