I’m sorry, I misread my own notes, the Update Interval is indeed showing the past value.
The default Chrony config for “maxpoll” is 10. But that 10 is really the exponent of 2, so the default maximum polling time is somewhere in the range of 2^10 or 1024 seconds, around 17 minutes. I haven’t figured out the “why” yet, but occasionally Chrony bumps up the maxpoll value by 1 making the new interval in the neighborhood of 2048 seconds, or a little over 34 minutes.
To quiet things down we can either increase the WARN alert time to 36 minutes, or change the Chrony “maxpoll” to 9, so when Chrony does that weird bump-up it will still be within the check_mk OK time period.
If someone is truly relying on super-precise system clocks all of these settings are way too big.
I’m going to change my maxpoll to 9 and see how my interval numbers change.