Chris writes: I use Time Machine to back up my Mac’s data and I always want to know if the most recent backup was completed successfully and when it occurred. How can I monitor this?
The simplest way to check the status of your most recent Time Machine backup is to click on the Time Machine icon in your Mac’s menu bar or visit the Time Machine System Preference pane. These locations will tell you the date and time of the last successful Time Machine backup.
Note that OS X 10.8 Mountain Lion now allows users to designate multiple Time Machine drives, and will alternate backups between each designated drive. The Time Machine System Preference window will identify which specific drive was last used for backup and when.
Users looking for a more customized approach can also use a Terminal command to reveal the last backup date and time.
Open Terminal, enter following command, and press Return:
defaults read /private/var/db/.TimeMachine.Results BACKUP_COMPLETED_DATE
This will return a time and date value, with the time referencing Coordinated Universal Time (UTC). In the example below, the last successful Time Machine backup occurred at 13:12:34 UTC (9:12:34 AM EDT) on Friday, October 5, 2012.
While the terminal command is at first glance just a more complicated method of determining the last backup time when compared to simply checking the Time Machine menu bar icon, using Terminal opens up additional options. Users can write AppleScripts or other custom workflows that call the Terminal command and trigger email notifications or other system tasks.