Glossary
Mach continuous time
The macOS clock, counting from boot and including sleep, used for Unified Log timestamps before conversion to UTC.
Mach continuous time is a monotonic clock that starts at boot and keeps counting during sleep. tracev3 entries store their time as continuous-time deltas from a base, not as a date. On Intel Macs one tick is one nanosecond; on Apple silicon the timebase is 125/3, so ticks must be multiplied by 125 and divided by 3 to get nanoseconds.
timesync records map these values to wall-clock time for each boot. log show --style ndjson shows the raw value as machTimestamp.