How Time Machine manages its file archive and how it affects what you can restore<article>
<section class="page">
<p>Time Machine is an archive rather than a backup, because it retains multiple versions of files as you change them. That’s useful, because if you’re editing an image, a word-processing file, or another document, you can use Time Machine to restore a version before you made certain changes.</p><p>It always maintains at least one copy of every file, no matter how many times it’s revised, and if Time Machine has just a single version, it’s
always the latest copy. If a file is never changed from its initial backup, Time Machine never deletes it, either.</p><p>Apple has Time Machine automatically consolidate snapshots. It’s set to run every hour, making a copy of any file changed from the previous 24 hours. After 24 hours, Time Machine deletes hourly backups, but keeps one per day. After a month, it deletes daily backups, but retains one weekly snapshot.</p><p class="jumpTag"><a href="/article/3431165/understanding-how-time-machine-manages-its-file-archive-and-how-it-affects-what-you-can-restore.html#jump">To read this article in full, please click here[/url]</p></section></article>
Source:
How Time Machine manages its file archive and how it affects what you can restore
