For federation, follows and approvals are passed between servers and public events are federated between servers running our software. Over time, we hope to use #ActivityPub fully to trade data with other event software.
And some things we didn't mention! Many rough edges and a lot to do, but if you are interested or just want to let us know what you think of the idea get in touch. There is more on our website: https://www.theoccasionoctopus.net/
We support events in different time zones, and let people browse in any timezone they want.