I dusted off an older MacBook to prepare it for a new user. The battery was completely dead as it had been sitting in my desk drawer for over a year. I let it charge for ~15 minutes before powering it on and holding Command + R to boot into recovery.
Next, I clicked Reinstall Mac OS and was presented with a drop-down UNTRUSTED_CERT_TITLE. If you run into this try clicking Utilities from the top toolbar and open the Terminal.
With the terminal open run the command date. If the date is incorrect, this is your problem!
The easy fix is the set the correct time. Run ntpdate -u time.apple.com in the terminal and let Apple do the work for you. Run the date command again to confirm the time is now correct. Jump back to the Reinstall Mac OS and you should be good to go!
NOTE: Be sure you have a network connection. Check
Utilities->Network Utility.
Cheers! 🍻