I use chrony to keep my home linux server synced with public NTP servers.
It’s fun to watch which servers have the lowest latency and estimated error.
For me the lowest latency is Facebook’s Public NTP.
It’s easy to think time3.facebook.com has the highest estimated error. But no the unit there is us or μs meaning microseconds, so this is 6.4 milliseconds.
All this on the cheapest cable internet connection available. :)
$ chronyc sources -v
.-- Source mode '^' = server, '=' = peer, '#' = local clock.
/ .- Source state '*' = current best, '+' = combined, '-' = not combined,
| / 'x' = may be in error, '~' = too variable, '?' = unusable.
|| .- xxxx [ yyyy ] +/- zzzz
|| Reachability register (octal) -. | xxxx = adjusted offset,
|| Log2(Polling interval) --. | | yyyy = measured offset,
|| \ | | zzzz = estimated error.
|| | | \
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^- time1.facebook.com 1 10 377 806 -1083us[-1059us] +/- 34ms
^- time2.facebook.com 1 10 377 197 +8361us[+8385us] +/- 76ms
^* time3.facebook.com 1 10 377 83 -708us[ -683us] +/- 6466us
^- time4.facebook.com 1 10 377 40 +4300us[+4300us] +/- 25ms
^- time5.facebook.com 1 10 377 610 -918us[ -894us] +/- 19ms
$ chronyc -n sources -v
.-- Source mode '^' = server, '=' = peer, '#' = local clock.
/ .- Source state '*' = current best, '+' = combined, '-' = not combined,
| / 'x' = may be in error, '~' = too variable, '?' = unusable.
|| .- xxxx [ yyyy ] +/- zzzz
|| Reachability register (octal) -. | xxxx = adjusted offset,
|| Log2(Polling interval) --. | | yyyy = measured offset,
|| \ | | zzzz = estimated error.
|| | | \
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
^- 2a03:2880:ff0b::123 1 10 377 808 -1083us[-1059us] +/- 34ms
^- 2a03:2880:ff0c::123 1 10 377 199 +8361us[+8385us] +/- 76ms
^* 2a03:2880:ff08::123 1 10 377 85 -708us[ -683us] +/- 6466us
^- 2a03:2880:ff09::123 1 10 377 42 +4300us[+4300us] +/- 25ms
^- 2a03:2880:ff0a::123 1 10 377 612 -918us[ -894us] +/- 19ms