How to Fix This Copy of Install OS X Can't be Verified

If you've ever tried to reinstall macOS on an older Mac that hasn't been used in a while you have have come up against the message "This copy of Install OS X can't be verified. It may have been corrupted or tampered with during downloading." and the installer refuses to run.
In fact, the problem isn't with the installer at all, it's likely due to an incorrect system date in the computer. In this video I explain how to fix it.

Music: Legacy of None by Harris Heller from StreamBeats.com (Copyright Free).