Re: Mains powered clock
Just check your clocks & watches against the computer these days. That gets synced to some nice atomic clocks somewhere.
Last time I checked (a few years ago, and I can't be arsed wading through that crap again to see if it's changed), Microsoft trumpeted their embraced and extended version of NTP (after ignoring NTP for 25 years first). After making many "improvements" they guaranteed your computer would show the time correct to ±2 minutes. I could have misremembered that, and it could be that timestamps would have that slop but the displayed clock would do better, but it's still shit. Maybe they've improved things since I looked.
On Linux, using the default NTP servers specified by the installation, I'd be surprised if the time it showed was less accurate than ±50 ms. If I were to configure ntpd to use a few stratum-1 servers (that would be naughty, so I don't do it) I could do better than that.
For those without sane implementations of NTP, every so often Aldi sell a small MSF clock for around a tenner. Or you could install an NTP client app on your phone. Or even tell your phone to get its time from the MNO (not as good, but probably better than Microsoft's "improved" NTP - I just checked and it's about 2s slow).
Biting the hand that feeds IT
