Archiving does have a date, but the date just isn’t shown the UI (and can’t be set by the user) at the moment.
Obviously, it is also already possible to provide a revision comment as part of the asset update that archives it.
So the simplest change might just be to expose the archived date in the UI.
More broadly though, I think something like this could be useful when there is additional (structured) data that needs to be associated with the transition of an asset to the archived state. I think @Farmer-Ed has some log types like this for his animals.
This also reminds me a bit of what I was alluding to with the “axioms” I wrote out in this post.
i.e. the concept that more fields on assets could (in theory) be generalized to be the result of the associated logs - just like inventory, group membership, and location/geometry are today.
I’m a little less sold on that generalization making sense for all fields now (given how much complexity the existing cases already hold and that asset versioning is on by default in farmOS), but perhaps archived date is a special case.