Have you ever tried to install OS X from a USB Flash Drive and received this error message?

This copy of the Install OS X Mavericks application can’t be verified. It may have been corrupted or tampered with during downloading.

The issue is not with your installation media, but rather with your Mac’s time and date. Follow these steps to set it right.

  1. While booted from your OS X Install Media, launch the Terminal from the Utilities menu.
  2. Enter the date command to report your Mac’s known time and date.
  3. If the time and date are not correct, you can set it using the date command.
  4. Follow this format date mmddHHMMccyy where mm equals month, dd equals day, HH equals hours, MM equals minutes, and ccyy equals year. (Example: Today’s date would be 120310002014.)
  5. Press Return, and your Mac will confirm the current time and date before the prompt.
  6. Type exit or press “Command + Q” to quit the Terminal and resume the installation process.

I first started seeing this error message in OS X 10.9 Mavericks, but date verification may be present in older versions of OS X. When ii doubt try setting your computer’s data to the year your version of OS X was released. For a complete listing of OS X release dates visit the Robservatory.