Found via a link to https://gonium.net/blog/2010/10/24/smart-meter-datenkabel-selbst-gemacht--libehz/ from https://wiki.volkszaehler.org/software/sml

"Bringing Nixie tubes back to life" - small manufacturer of Nixie tubes and clocks in Březolupy, Czech republic, https://www.openstreetmap.org/search?query=B%C5%99ezolupy#map=13/49.11641/17.61486
Found on Jamie Zawinski's blog https://www.jwz.org/blog/2024/09/cathode-poisoning/, https://www.jwz.org/blog/2024/09/cathode-poisoning/#comment-252180

Information about time(zones), dates, calendars and astronomical events.

PTP time on a Raspberry Pi CM 4. Note that the Rpi 5 also has PTP support.
See also https://www.jeffgeerling.com/blog/2022/ptp-and-ieee-1588-hardware-timestamping-on-raspberry-pi-cm4
https://store.timebeat.app/collections/timecard-mini
He mentioned another time-related HAT on his video https://m.youtube.com/watch?v=RvnG-ywF6_s

https://www.jeffgeerling.com/blog/2023/build-your-own-private-wireguard-vpn-pivpn is interesting too.

Found via the COFF mailing list https://www.tuhs.org/pipermail/coff/2023-August/001663.html
See https://hack.org/mc/blog/nts2.html about NTS, a secure version of the network time protocol
https://hack.org/mc/blog/no-more-x11.html about Wayland
https://hack.org/mc/writings/xkb.html about keyboard mapping

Keep accurate time on a Linux machine based on radio time signals such as DCF77, MSF or WWVB. Found via https://packages.debian.org/stable/net/radioclk
It uses the modem control input signals to monitor the signal from the radio receiver. For a Raspberry pi, where I want to use this, the articles
"Raspberry Pi RTS / CTS Flow Control" https://ethertubes.com/raspberry-pi-rts-cts-flow-control/ and
"Raspberry Pi 3 Hardware Flow Control"  http://www.deater.net/weave/vmwprod/hardware/pi-rts/ will be useful.

The tinyPFA is a Phase Frequency Analyzer, it is a portable, battery operated, two input device with a 4 inch display that can measure very precise frequency and phase differences between the signals applied to both inputs. The input frequency can be any frequency between 1 MHz and 300 MHz. Typical use is to measure the differences between two 10 MHz clocks. The tinyPFA can numerically display the phase and frequency difference, show the measurement in a graph versus time, store the measurements on a SD card inserted into an SD card slot, or send the phase measurements over USB to a PC, running a program such as TimeLab, for further display and processing. Phase and Frequency measurement accuracy is better then 1e-12 divided by the measurement time in seconds with decimation set to 1 Be aware the maximum frequency difference that can be display depends on the measurement time (Tau) and is approximately 0.4 / (Tau in s) so for Tau is 1 s it is 0.4 Hz maximum difference.

Blog, mostly about network-related things. Found via https://www.tuhs.org/pipermail/tuhs/2023-March/028267.html
Time is an illusion, Unix time doubly so... https://www.netmeister.org/blog/epoch.html
Sharing Secrets https://www.netmeister.org/blog/sharing-secrets.html

Roughtime is a protocol that aims to achieve rough time synchronisation in a secure way that doesn't depend on any particular time server, and in such a way that, if a time server does misbehave, clients end up with cryptographic proof of it.

“Rough” time synchronisation means that, at this stage, we would be happy with time synchronisation to within 10 seconds of the correct time. If you have serious time synchronisation needs you‘ll want the machinery in NTP or even PTP (which needs hardware support to do right). There’s no reason why Roughtime shouldn‘t be (almost) as precise as NTP, but the use cases that we have in mind for now don’t need much precision. For example, about 25% of certificate errors shown by Chrome appear to be caused by bad local clocks and we don't need much precision to fix that.

Found via Cillian O'Driscoll's fork https://github.com/odrisci/roughtime
See also https://github.com/oreparaz/vroughtime for a simple client written in C.