This message can appear if the date and time aren't set correctly on your computer. Use these steps to check your date and time, then try installation again. 

Check your Date & Time System Preference by following these steps:

1. Quit the OS X Mavericks installer.
2. Choose "System Preferences" from the Apple menu ().
3. Click the "Date & Time" icon in the System Preferences window.
4. Click the "Date & Time" tab in the System Preferences pane that appears.
5. If the padlock in the lower left is locked, click it and enter an administrator name and pasword when prompted.
6. Make sure the "Set date and time automatically" checkbox is selected and the appropriate region is chosen in the field to the right of the checkbox.
   Alternatively, manually set the date and time to an accurate setting (for example, the date should be set later than Oct 1, 2013).

Re-open the Install OS X Mavericks app (located in the Applications folder) and proceed with installation.