When I try to create a numerical tag, i.e. 2026, it works, if there isn’t a tag using same ID 2026. If that ID is in use, I get that tag instead of 2026.
I’m quite sure that is an old bug, that is fixed at some point. Or do I remember wrong and I should not use numerical tags at all 
Anyway, I count that as a bug — and I would like very much use years as tags.