El Capitan installer error: OS X could not be installed on your computer #

Among the least helpful error messages I've come across:

OS X could not be installed on your computer

No packages were eligible for install. Contact the software manufacturer for assistance.

Quit the installer to restart your computer and try again.

Restart

It should read "Fix the time and date before installing" or something like that. Here's how to resolve while booted from the install disk:

Utilities > Terminal
Fix the date and time, e.g., date 101407002015 (i.e., Oct 14, 07:00 2015)
Click Restart (UPDATE: Newer macOS installers like 10.15 Catalina do not require rebooting to continue.)

/mac | Oct 14, 2015

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