ntpsec.anastrophe.com

Attention:
This service is shut down for general clock sync. I'll still accept peering requests, but service availability isn't guaranteed. I'm no longer running dual timeservers on battery backup: no more four-nines availability (so sad).

NTP and SNTP service is available on port 123. Sorry, no IPv6 nonsense for me.
NTS service is available on port 4460. Use domain name nts.anastrophe.com.

You can verify the NTS cert here: What's my chain cert
And third-party verification of the time is here: Web Wiz NTP server test tool

Access policy: While I don't offer access for public use, I also don't block public use as a default. However, I provide this service for free, and your use is governed strictly by whether you abuse the service: Overly aggressive connections will be blocked. What is overly aggressive? Sync no more frequently than once every five minutes, absolute maximum frequency. Use ten minutes or higher and we can be pals. Commercial use is strongly discouraged. If your time needs are more critical than that, run your own timeserver. It's not that hard. Contact me at ntp@anastrophe.com if you need further clarity.

ntpviz generator (this server):

Raspberry Pi 4 Model B Rev 1.5, 4gb ram
OS: Raspbian 11.x - Bullseye
Webserver: NGINX
Monitoring: Monit (highly recommended)
Roughly 5 minutes once per hour to generate all graphs

A portion of the journey here: (outdated), and a more recent configuration (now only one timeserver).

ADS-B - Flight Tracking For Fun And No Profit

Most of the time, only one of a-ntpsec or b-ntpsec will be 'up'. I swap one or the other in place if significant downtime is necessary for maintenance.