You mean, like attempting to merge contradictory states? You will need some resolution stategy then, but in general that would be application-specific, and sometimes it may not exist.

Okay... But we're now back to invalid states being possible. Tagging with time isn't enough.

It isn’t enough for what? What are you trying to do?

There may be a way to solve whatever problem you have, but without specifics it’s impossible to tell.