This weekend, I noticed that the spinning hard drive in my MacBook Pro was dying. I ordered a replacement, installed it, then proceeded to install Yosemite. After counting the numerous Yosemite installer bugs, I noticed an unusual one:
This copy of the Install OS X Yosemite application can’t be verified. It may have been corrupted or tampered with during downloading.
My searches for this didn’t yield a useful solution so I figured out what the problem really was: Since I disconnected the battery as part of my install process, the computer was completely without power for a moment and loss the date/time. So, I set the date in the terminal using the date command, and then the above mentioned error went away.
Note to Apple: If you are trying to verify a signature and it fails, you should check to see if it failed due to a bad date on the cert. If so, then you should prompt the user for the date/time instead of putting a cryptic and incorrect error message on the screen.