Comment by adrian_b
3 years ago
I have not checked if in recent versions of Windows there has been any change, but previously by default the computer clock was synchronized with a time server only once per day, so until the next synchronization it is normal to accumulate a time difference up to one or two seconds.
I do not know how many Linux distributions enable by default a ntpd daemon, but I have always enabled it on any computer running Linux or FreeBSD.
When a ntpd is active, it adjusts continuously the local clock based on comparisons with NTP servers, so the time cannot be wrong by more than a few milliseconds. Therefore the error becomes 100 to 1000 times less than without ntpd.
The time differences between computers using NTP on the same LAN are smaller, usually of a few hundred microseconds. For even better synchronization within a LAN, the Precision Time Protocol must be used.
If you have systemd it enables a timesyncd service which is NTP.
To be precise, it's SNTP, not full-fledged NTP:
> The systemd-timesyncd service implements SNTP only. This minimalistic service will step the system clock for large offsets or slowly adjust it for smaller deltas. Complex use cases that require full NTP support (and where SNTP is not sufficient) are not covered by systemd-timesyncd.
SMTP is really only intended for use in edge-of-graph instances where there is no further dependence on the output e.g. a wall clock. General-purpose computers should all be using NTP.