Apparently based on Mach absolute time, log entry times are converted to wallclock times. This exposes them to the vagaries of time zones, seasonal adjustments, and periodic wallclock adjustments. Here’s how all that works, and can confuse.
Ulbow
An introduction to the Unified log used on Macs and Apple’s devices. Its goals, how logs are stored and maintained, their content, privacy protection, and tools available to access them.
Wrangle Unicode normalisation, discover all the app extensions in your Mac, browse the log with nanosecond times, and preserve documents versions when moving them.
If you only have access to the log files of a Mac or device and can’t create a logarchive of them, this new build offers a solution, plus detailed info about a logarchive to help you browse its contents.
LogUI can now read and browse saved logarchive packages, including those from other Macs, and iOS and iPadOS devices.
You can now save log extracts to JSON files, which LogUI can read in as a log extract. Also a new Reduce tool to filter unwanted log entries.
This compares short time intervals obtained from log entry timestamps obtained from the log show command via Ulbow, those from LogUI using OSLog, and Mach Absolute Time.
By default, the log show command and Ulbow display log entries using the time zone set when they were written to the log. Bringing consistency in a new build of LogUI.
It turns out that ‘nanosecond’ times introduced in LogUI are largely artefact. Is higher resolution timing really needed, and how can it be obtained?
Although there are important differences between Intel and Apple silicon Macs, both can resolve time to nanoseconds. So can this new version of LogUI.
The Eclectic Light Company 