[chrony-dev] chronyd 3.5 on macOS

["Gerriet M. Denkmann" <gerrietm@xxxxxxxxxx>]

macOS seems to have two clocks:
• a hardware clock, which always runs (even if the device is switched off)
• and a software clock, which is used by all apps.

When the device starts (or awakes from sleep) the software clock is set from the hardware clock.

The problem: adjtime (or whatever chronyd uses to keep the software clock synced with ntp) does *not* update the hardware clock.
The only way to set the hardware clock I know of is settimeofday.

Assuming a computer where the hardware clock drifts with 17.36 ppm (= 1.5 sec / d.
After a month, after each wake-up the time will be 45 sec off; which then takes chronyd 3 or more hours to set correctly.

Workaround:
• have a launch daemon, which, whenever the system is going to sleep, does gettimeofday + settimeofday.

Would it be possible that chronyd does this? 
Alternative: just do settimeofday periodically (e.g. every 15 minutes or so).

Gerriet.


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