Q: I tried installing mavericks and i always get "This copy of the Install OS X Mavericks application can't be verified. It may have been corrupted or tampered with during downloading."

Found this post and it worked for me!

http://www.ordinarycoder.com/copy-install-os-x-mavericks-verified/

I know this is a stupid question but I'm new to Apple OS's - how do I find the downloaded OS X file to delete it? I've looked in files but don't see it.

I had this same problem.  I tried verifying and repairing disk, but the thing that finally worked for me was to start my download on a different internet connection.  I used the 3G on my phone to download the first 50 mb, pressed pause and then finished on my home connection.   

Thank you very much Bill!

In case anyone at Apple is listening in. ...)

This error is probably due to an invalid certificate if the system date is in the past.

Please fix this in the Yosemite binaries. It must be causing headaches for many people.

Michael

I also had the same problem when I tried to install Yosemite from the USB Flash drive. The same error message. Turns out, for some strange reason my MBP 17" system's clock was "stuck" in year 2000. Had to use Terminal to adjust date (https://bensmann.no/changing-system-date-from-terminal-os-x-recovery/), then restarted Yosemite installation and no problems.

thanks hugely to bill & jonathan.

the date change can be done through system prefs/date & time – turn off "set date and time automatically", then reset date. (revert once the job is done, obviously.)

i am presently using this fix for yosemite, so the built-in problem endured for at least one further iteration.

many thanks bill_04!

Is just this. Easy it worked. Thanks for the help.