In order to return your Macintosh computer to an earlier version, How to Restore a Mac to an Earlier Date you must have backup information stored on an external hard drive. Time Machine is a program for Macintosh computers that allows you to restore individual files and folders, as well as the entire system, by using the backups saved on your computer’s external hard drive.
Losing important files on your computer can be a real pain, especially if you don’t have a backup. When your computer’s system or startup disk is damaged, the only way to get your lost data back is by restoring your system from a backup.
Before you restore your computer to an earlier date, make sure you backup your current files, as some may be lost during the restoration process.
In order to connect your external hard drive to your computer, simply insert the USB cable into an available USB port.
Before you can begin using your Mac, you need to install the Mac OS X operating system. To do this, insert the Mac OS X Installation CD into your optical drive and double-click the “Install Mac OS X” icon.
Your computer will open the Installer window once it powers on. To begin the restore process, click “Utilities” at the top of the screen and select “Restore System from Backup” from the drop-down menu.
Click “Continue” to proceed, and click the “Time Machine Backup” volume icon.
Choose the backup you want to use to restore your system, and click “Next.” The backup restoration process can take up to 45 minutes to finish, depending on the size of your hard drive. Once it’s done, click “Restart” to restart your computer.