Below is the release date for your favorite PowerPC and Intel-based Operating System from Apple and due to expired certificates on the installers, you will need to set the date to match (or within a year of the release dates) using the Date and Time Preferences in macOS, the Terminal or from the BIOS and then install normally.
Be sure to have a smartphone or tablet handy since adjusting the date will cause websites with SSL certificates to not load at all until the date is made current. Please note that if you are installing with the use of virtualization software, you need to disable the option to sync the time.
Failure to disable the sync will cause the time to sync from the host. If you are unable to find the settings, your last option is to change the time on the host (which will limit your internet access there) and set it to not update until your virtual session does the first restart.