Bump MikeVerk's SOLUTION up!
I had created a USB installer at least 6 months ago. It had worked until this week on multiple Macs (I'm in IT). After recreating a bootable USB using DiskMaker X 5, the same error would occur. I checked the time and it showed the correct time in PST even though I'm in MT. MikeVerk pointed out that by setting the date BACK to sometime soon after the installer was downloaded, resolved his issue. I did the same.
My copy of El Capitan, located in my Applications folder, had a date created of Oct 9th, 2015 and date modified of Dec 4th 2015. While booted into my USB, I opened terminal and set the date/time to 9:30AM Dec 4th, 2015 (just in case the date modified matters).
As I type this, the install is finishing up.
Nice going all!