I have done some more work on setting up a system to keep the system clock on the OSD accurate. I'm hoping others will be able to benefit from this. The method I use is based on the assumption that you have the OSD on a home LAN, and have a PC (either Windows or Linux) connected to the same LAN, and that the time on the PC is kept accurate (generally by having it sync regularly to some external time source). I actually use a Windows PC for this, but it should also work with Linux, as the main program is written in Expect, which is a native Unix/Linux program. I am using a Windows port of it. I also use WinCron, a Windows port of the standard Unix "cron" facility to do the regular scheduling of the Expect script.
Anyway, look in
http://www.xmission.com/~gazelle/OSD_timesyncEverything needed is there - please post to this thread if you have any questions or comments.