Q: Corrupted Sierra OS

Verify your preference in

>Sys Preferences>Date & Time>Set Date and Time automatically

This can help the server recognize your region for authentication  for the download installer

Or it might be the next setting panel the ”Time Zone” / as the one you suggested didn`t work. You have to allow apple to localize you exactly. After two failed attempts, I`m giving a try with the setting time after your location checked.

Little later.

Well... it looks like neither of these works. I cannot have sierra installed on a iMac 2015. Holy caramba! I still have Ubuntu on a stick.

I am having this very same issue on a Macbook Pro Retina 15in late 2013. Installed flawlessly on my Mac Mini 2012.

Step 1. Go to your applications folder.

Step 2. Find the installer for macOS Sierra.

Step 3. Right click on the installer and click "Show Package Contents".

Step 4. Click on folder named "Contents".

Step 5. Click on the folder named "SharedSupport".

Step 6. Delete the file named "InstallInfo.plist".

Step 7. Enter your administer password to confirm.

Step 8. Now open the installer.

This work flawlessly, thank you very much for your help!

Your welcome!