there is definitely a timeserver on our LANs. agreed.
but I don't know them (yet). I could probably get time from a default router (etc) but since port 80 'always works', this seemed like a trouble free way to get time, at least within a few seconds.
I like having several fallbacks. using ntp or ntpdate would be a first try; if that times out, then try other methods, which could include hitting a webserver that is known to keep time. ebay is a great example since they NEED to be synced and they are big enough to be trusted to keep proper time
there is also something called 'nist-80' which does not look like a standard (yet) but is supported by some vendor code (non-free, I think). that gave me the idea to try to get time over port-80.
I don't mind 'wasting' a rasperry pi for this. its cheap, its fanless and it can do any of these tricks.
the rasp-pi box will have a usb connection to my arduino nano and maybe every half hour or so, it will push updated time across the serial connection and the arduino will just pick out the ascii HH:MM:SS and set the clock from that, directly.
I'll post a follow-up once its implemented, in case anyone cares.