Time should be universal, simple, and precise. Not in computers, though. Given enough clocks, it can behave oddly at times.
macOS
View the same log entries at different times, and their timestamps change. This explains why, and what is going on.
When Time Machine seems to take a long time preparing the next backup, or gets stuck, here is how to diagnose and deal with it.
Why was my Mac still preparing a backup 20 minutes after it should have been completed? And what is a ‘deep event scan’?
Two major tools are available to help you deal with problems. Here’s how to use them to best effect.
Is Time Machine becoming erratic? A simple diagnostic process can establish what the problem is, and how to deal with it.
Here are two log excerpts which should be identical, but only one out of all the entries is actually the same. What is wrong?
Working out why Time Machine backups go wrong isn’t necessarily that different from unravelling classical mythology. In some ways.
Getting deeper into using Sierra’s new logs, and investigating why Time Machine backups become irregular.
Devising strategies for getting the best out of Sierra’s new logs. Or should we just abandon them as a lost cause?
