From Newsgroup: comp.sys.raspberry-pi

David Taylor <david-taylor@blueyonder.co.uk.invalid> wrote:

On 22/07/2021 09:32, A. Dumas wrote:

That's because of the switch to systemd. An ntp (-like?) service is still
installed. Its interface is "timedatectl" which gives a status overview.
See man timedatectl.

It seems to sync often enough by itself that my Pi4 (without an rtc) which >> is always on and which I don't monitor is accurate to within about a second >> compared manually to this iOS device from which I just logged in. So, I
don't think it's a good idea to install the ntp service on top of that; not >> without first disabling this new stuff.

A "sudo apt-get install ntp" fixes the lack of NTP on all my RPi cards. No problems at all even with the latest OS. Personally I prefer to trust the reference NTP version rather than some other version, and it has the advantage
that I can manage it in the same way as NTP on Windows and other Linux systems.

Here I see accuracies well under a millisecond even when syncing over Wi-Fi -
e.g. a Raspberry Pi 400:

https://www.satsignal.eu/mrtg/raspi24_ntp-b.html

and when you activate the GPS/PPS option, well under 10 microseconds even with
a Raspberry Pi 1B:

https://www.satsignal.eu/mrtg/raspi1_ntp.html

Here's a Raspberry Pi 4 with the Uputronics GPS/PPS/RTC HAT:

https://www.satsignal.eu/mrtg/raspi25_ntp.html

The antenna is a mag mount puck, indoors, on top of some mains trunking. Something like that can be your stratum-1 source so many local clients.

I'm comparing file timestamps with another system in the Netherlands and having
sub-second accuracy makes the comparison much more certain. I appreciate that
your requirements may be less stringent, but you can have a lot of fun with NTP
and GPS!

Er, my "about a second" was from me simply glancing at two devices. I'm
sure the actual accuracy is the same as for reference ntp, because it runs this: https://wiki.archlinux.org/title/systemd-timesyncd

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