I'm still in the process of tagging pages that were migrated from the old site, so for now you're best off using the search engine rather than relying on the tags.
- How to search events in Lightning calendar - To search events in the Thunderbird (10.0.3) Lightning (1.2.b1) calendar extension: Select the calendar tab. Events and Tasks -> Find Events. They should really add a search button next to the tasks icon (top right) as they have with email.