I ran into an issue where performing a clean install of OS X Mavericks produced an error "This copy of the Install OS X Mavericks application can't be verified". It may have been corrupted or tampered with during downloading."
I was performing the install from a USB stick, as well as performing the install on a machine that was not connected to the internet (wired or wireless). After recreating the USB installer, and getting the same results, I started to suspect that it was attempting to perform a check against the installer itself, so I wired it up; same thing. Then it hit me, it's checking against a certificate, date and time must be off.
Dropping into Terminal from the Mavericks installer (Utilities > Terminal) and running the date command showed that indeed the date and time were not current.
I simply ran the following command below to set it to today's date (Oct/26/2013 13:15)
After the date is set, close terminal and proceed with install, this time successfully :). HTH