I'm running Ventura 13.4 on an M2 MacBook Air. I run the FT8 and FT4 digital modes for ham radio.
FT8/4 requires fairly accurate time synchronization. It seems that macOS gets out of sync when waking up from sleep. (See Time.apple.com sync).
The solution for better time synchronization is to run chrony, or better, the GUI version, chronyControl. (See Accurate time keeping on an Apple Mac running macOS Big Sur for FT8, FT4 and WSPR)
This has been working well for me, very well. My clock is very accurate. However, I'm still having time-shift issues. Notice that the time.is website says my time is +-0.001 seconds. But look at the left-hand side, the third column is my time shift compared to others, the rest of the world is about 0.8 seconds off.
Since it is unlikely that the rest of the world is wrong, I must be wrong. Other hams have steered me to the likely culprit: I have an audio latency issue. The audio setup is simple and fixing it is unlikely. So I'd like to be able to bump my system clock by fractions of a second. (Clearly, I'll have to disable chronyControl when I do this!)
Any sort of shell script to read the time and set the time would probably not work well since it would take a fraction of a second to run. I need a better way to do this.
How can I bump my system clock by a specified amount?