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Tech Tip: ‘An Error Occurred While Preparing the Installation’ Fix

Having worked in Technical Support here at OWC for some time now, I have helped customers handle many different types of errors and problems that they have come across. Some such as, “The disk you inserted is not readable by this computer,” might have simple solutions like formatting the disk, and some are more difficult such as “My Mac keeps freezing. Help!”

Related: My Upgrades tool helps you get the most from your Mac

One error that customers often come across while upgrading their machines occurs during the re-installation of macOS or OS X, and it has a relatively simple fix.

Once booted into the recovery partition and after selecting “Reinstall OS X”, the “Eligibility Verification” window shows up. The error occurs as soon as you click “continue”. An unspecified error shows up which states “An Error occurred while preparing the installation. Try running this application again.” Upon doing so, the same exact error pops up. Nothing has been done to have this occur, so what exactly is going on?

Screenshot of "An Error occurred while preparing the installation" popup window

While this can be frustrating, something quite simple is going on in the background that needs to be addressed. One of the checks that occur during “Eligibility Verification” is to see what time the machine thinks it is. If the computer is reporting the wrong time, an error will occur.

While there is a simple fix, it does require using the Terminal to accomplish. Many users might be wary of the Terminal, feeling like something could break and that it’s something only hackers and System Administrators use. While this can be true, the Terminal can be your friend and help you to resolve quite a long list of issues that commonly occur. But with great power comes great responsibility. Terminal can be destructive if its abilities are improperly used. My recommendation for those that are wary of this wonderful tool is to copy/paste commands or to type them very carefully and to double-check what was typed before execution.

To fix the aforementioned “unspecified error”, follow the steps below:

  • First, click “OK” on the error window.
  • Then click on “Utilities”, then “Terminal”.
  • Once opened type in “date” without the quotes and hit enter. This will give you the computer’s current time and date.
  • To fix the date, type in the current date/time in the following format: “date mmddHHMMyyyy”. (mm = two-digit month, dd = two-digit day, HH = 24 hour, MM = minute, yyyy = 4 digit year) So if it is currently 10:46am, June 19, 2015, the command would look like: “date 061910462015”.
  • Once you have the current date/time inserted, you will then hit enter. You can double-check to see if it was set properly by using the “date” command once more, it should show the date/time you have just typed in (see image below).
  • Once the proper date and time are set on the computer. Exit the Terminal and run the OS X installer once more. This time it should go through without any errors! If it doesn’t, feel free to contact an OWC technician for further assistance.

Screenshot showing the terminal command to change the date on a mac


Looking to Downgrade from one OS to another? We have you covered!

More tech tips from OWC

Look for many more tech tips on macOS Yosemite, El Capitan, Sierra, High Sierra, Mojave and Catalina for your Mac or iDevice at the Rocket Yard!

OWC Robert J.
the authorOWC Robert J.
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  • Wow, got me past that point and was not expecting it. Thank you! Now dealing with “this item is temporarily unavailable”.

    • FYI the fix for the “this item is temporarily unavailable” screen after putting in my Apple ID was to put in my husbands, who’s computer it was. Although he was not the the original owner it still worked.

  • Robert, thanks for the date suggestion. I use that frequently to do other Mac OS installs. I tried the suggestion that you provided above. It did not work. I keep getting “An error occurred while preparing the installation try running this application again.”
    I’m trying to install Yosemite 10.10 from the install disk.
    Any suggestions?

    Thank you.

  • wow, after hours of trying to figure this out with bootable usbs, networks, internet restores, changing the time is what worked? Go figure, serves me right to think I could do it myself.

  • Good day

    Sorry to bother you. I have a MacBook propro running OS X Yosemite and version 10.10. 5

    It keeps giving me error messages when I try install softwares

    (installation error message An Error Occurred While Preparing the Installation)

  • Thank you so much I just fixed up a MacBook Pro for my girlfriend and I was trying to see if everything was working smoothly and this popped up. You’re a lifesaver

  • I did all of the following options above even when I set upped the time and date correctly and try reinstalling the mac OS Sierra and I’m stillllll getting the same error “an error occurred while preparing the installation. try running this application again” What do I do pleaseeeee help

  • This worked perfect! Any idea why the mac wouldn’t get the time from the apple time servers? Seems strange.

  • Went all around the houses trying to resolve this and cant believe it took me till now to find the solution here!

    Still not decided if its positive/negative that it was so quick & simple.

    Thank you – My daughter now gets my Macbook!

    Do you have Patreon?

  • Its moments like these when I’ve no idea what to do to fix the problem that I find articles such as this, fix it in one fell swoop and then sit back and appreciate just how awesome the internet of information can be. thanks so much

    WORKED 100%

    • Totally agree. I’ve been on the phone with Apple for a long time today trying to fix this and this article fixed everything. I was skeptical it would work and it did!!!

  • THANK YOU!!!! I am pretty tech savvy and couldn’t figure out how to fix my old MacBook Pro that I couldn’t get in to…you are the ONLY site and article that helped…THANK YOU!!! This article rocks, as do you.

  • after signing in with my apple id. a message appears, “This item is temporarily unavailable. Try again later.” any ideas what that might be?

  • I have erased the hard drive on my iMac (Early 2008) and am trying to re-install El Capitan (10.11.6) that was running on it. It was acting up so decided a re-install was the best way to go. Followed the instructions and all went well until it it restarted. Message says” OS X could not be installed on your computer”, “No packages were eligible for install. Contact the software manufacturer for assistance. “Quite the installer restart your computer and try again.”


  • Thank you so much!! This error was driving me crazy and your fix was easy to follow and resolved the problem straight away.

  • This was the solution for me after hours of trying to reinstall in various ways unsuccessfully. Genius! Thank you.

  • Wow!!! I would vote myself as THE happiest girl on the planet right now!!! Thank you SO much for sharing this little sliver of knowledge with us! I seriously cannot express my gratitude!