invites from mail post to wrong day

when I click an attached event invite in Mail, Calendar opens an event from almost 3 years prior (Nov 2009). It does not add the event from Mail to Calendar at all.

If I move the attachment to my desktop and open it from there, it will add it properly, but if I accept the invite, it will send between 2 and 5 responses to the sender.

Anyone else experiencing this problem or know how it can be fixed?

Thanks!

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Mike