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While installing OS X El Capitan or OS X Yosemite, any of the two error messages “This copy of the Install OS X El Capitan application or OS X Yosemite can’t be verified” and “error occurred while preparing the installation” may display on your computer screen. If the file that you’re trying to install has been corrupted or tampered, you’ll receive these messages because in that case your copy of the OS will not be verified.

Whenever you see these messages while preparing the installation, try running again” error message because sometimes you may resolve the issue by the given details like by simply rebooting and trying to re-download/reinstall OS X again. If you have applied these tricks already and still the issue persists, it may be helpful to modify the system date of the Mac. You can fix these errors while basically any type of installation practice in OS X El Capitan or OS X Yosemite, either you’re trying to install a standard App Store update, to clean installs, Internet Recovery, or using a bootable installer volume on any specific Mac.

If you run into either an error message while updating or installing OS X while from an active OS X boot, by setting the Date & Time on the Mac to be determined automatically, you can typically resolve the problem. To do so, go to the Apple menu > System Preferences > Date & Time, and verify that you check the option “Set date and time automatically”.

One thing you need to remember and make sure is that your Mac should have active internet access while setting the time and date as “automatic”. If your Mac system doesn’t have the Internet access or this issue encounters while an alternative OS X installation method and it’s not possible to access System Preferences, the next option is turning to the Terminal to set the date.

Mac Error -1

To find out if the Terminal date trick can help you to successfully install OS X, and resolve those error messages, turn to the command line while at the “Install OS X” boot menu. Now click on the “Utilities” menu option to pull down all the options and select “Terminal”. Now type the following command into the prompt box:


Click on the return option if the reported date doesn’t match with the actual current date. It may resolve the problem if it’s been the possible cause of the problem. It may look like:


The entire line matters, so the date, and year must be correct in order to install Mac OS X because if the date is set before the date release of OS X, the issue will trigger. If you notice the above format of date, you’ll find it completely wrong. Year and month need your special attention to avoid committing such mistakes. So you need to set the current date and time using a variation of the same terminal command. To two so, you can apply any of the two approaches, either set the date via the internet, or do it manually. Setting it via the internet will be easy and better.


To set the date manually, make sure that you have the Internet access otherwise it won’t work. However, if you want to do it manually use the ‘date’ command again with the manual specifications.

It’s a little weird to use the manual date format, but if you’re familiar with the command line, you can retrieve it by yourself using date–help, which seems something like “[mm]dd]HH]MM[[cc]yy]”

Means you need to enter Month Date Hour Minute and Year as a solid line with no spaces or breaks between the numbers. For instance, to set the date as “September 20 2016 at 17:33” you would use the following syntax:

date - 2

This random string of numbers actually signifies month 09, date 20, time 1733, and year 16, combined.


Once you input the proper date and click on the return option, you will exit out of Terminal and start the installation procedure again as originally intended, and now OS X may no longer throw the catty sounding error messages.

Do you notice an error message explaining that “This copy of the Install OS X Yosemite application can’t be verified”. It may be possible that your copy have been corrupted or tampered while downloading” or may be the actual installer was modified or damaged while a download. To avoid this issue, make sure that you always download the OS X installer applications directly from Apple and the App Store. Don’t download it from any third-party site.

If an error occurred while preparing the installation, try a simple reboot and run it again to resolve the problem.