I started getting a damaged installer error today. I worked last week no issues.

Greetings kirbybj,

Thank you for using Apple Support Communities. It seems like you want to know if a certificate has expired. I would recommend you use this article to help troubleshoot the issue.

1. "Delete the installer. If it's a macOS installer, it may be in your Applications folder.
2. Check the date and time on your Mac to make sure they're set correctly. 
3. Download a new copy of the installer. If the new installer is also affected, please contact the maker of the software for help."

If an installer says it can't be verified or was signed with a certificate that has expired

Please don't hesitate to let us know if the steps resolved your issue or if you need additional assistance.

Take care.