OS X installation failure due to incorrect system date
“This copy of the Install OS X Mavericks application can’t be verified. It may have been corrupted or tampered with during downloading.”
May occur with other versions of OS X besides OS X 10.9 Mavericks as well, when attempting to install OS X from USB flash drive.
If the installation media is known good, the system date may be too far off for OS X to verify.
If the system time and date is too far off, within the OS X installation this may be fixed within the terminal window, using the command:
date to show current system date.
date mmddhhmmyyyy to set the date (month day hour minutes year).