If you encounter an error when trying to install a fresh operating system, it could be a problem with the date and time.
The other day a co-worker needed to borrow a Mac, so I grabbed an older MacBook Air from storage. I decided to wipe out the laptop’s flash storage and install a fresh version of OS X. I created a bootable USB flash drive installer, plugged it into the laptop, pressed the Option key as the machine booted, and then selected the USB drive as the boot disk.
I then ran Disk Utility to reformat the drive and then ran the installer to install OS X. It looked like things were moving along, until this appeared on the screen.
Error message while trying to install OS X from a USB installation disk.
I created another boot disk using a different storage drive, in case it was a hardware problem, but I got the same error. I figured that the fact that the laptop had been in storage for a while had something to do with it, and it did.
Note: This should work with OS X Mavericks and El Capitan. It also worked for me with the macOS Sierra Public Beta, which shows a different error message (“The installer payload failed signature check” pops up near the end of the installation) than the one that appears for El Capitan and Mavericks.
How to fix the problem
The installer checks the date on the computer. If the date isn’t current, you get the error above. The fix involves correcting the date on your Mac.
If you have an older OS on the Mac
If you have a complete OS on the Mac already, boot into it. Fix the date in the Date & Time system preference (Apple menu > System Preferences). Reboot using the USB boot disk, and you should be able to proceed with the installation.
If you don’t have an OS on the Mac
If you are in a situation like I was, and you don’t have a complete OS on your disk (you reformatted it), you’ll find that there’s no way to access the Date & Time system preference when you use an external USB boot installer drive. The Apple menu doesn’t give you access to System Preferences. You have to use the Terminal to set the date and time.
How to access the Terminal when you boot from an external boot drive installer.
If you use an external boot disk, you Mac starts up into OS X Disk Utilities. You can access the Terminal by clicking on the Utilities menu and selecting Terminal. Once the Terminal has launched, follow these steps.
- At the prompt, type to see the date that’s on the Mac. For example, here’s the date of the MacBook Air I worked on.
- If your Mac is connected to the internet, you can tell your Mac to check online for the current date and time. You can do this by typing at the prompt and then pressing Return.
You Mac should now have the current date and time. If you enter again (as I did in the screenshot above) the information that appears will be current. You can now run the OS installer.
If you don’t have an internet connection
You can still use Terminal to set the date. Go into the Terminal as described above, then follow these steps.
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At the prompt, type to see the date that’s on the Mac.
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Figure out the numerical representation of the date and time. The pattern you need to follow:
- Month: in two-digit format. For example, July is 07.
- Day: in two-digit format. For example, the 7th is 07.
- Time: in military format of hours and minutes. For example, 2:00 p.m. is 1400.
- Year: Last two digits.
- At the prompt, type , with being the representation you figured out. In my example, I typed . Then press Return.
In my example, the numerical representation is 0719140016. This stands for July (07) 19, (19), 2 p.m. (1400), 2016 (16).
The date should be set. You can check the date again by typing at the prompt. You can now run the installer.
This story, "Installing OS X: What to do when ‘this copy of the install OS X application cannot be verified’" was originally published by Macworld.
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