can this be modified

It can be done with a bit of custom coding.

Check if the event is a past event and then make the meta tag be injected in the header of the page.

Although I can’t help you completely out with your custom coding (I’m no coder myself, although I can read and write it a bit, I learn by a lot of trial and error, so there’s probably someone who can help you better with this) I hope you’ve got a bit of a direction where to look.

ok thanks, i was hoping it would be identified like the ( is_archive()
but they are post dates i need to see how event dates are identified.
Ideally i want to delete past events, but would rather get them de indexed first then delete.