@Graphista That's a slightly tricky one to answer, as butter doesn't often get to that stage in this household...it does depend on how many weeks over it is, and my parents were great believers in the "sniff" test or "try a tiny bit to see how off it tastes" test BUT more recent advice suggests that isn't always safe, as we've learned more about bacteria.
(Parents, uncle and aunt all grew up in the war so tried their very hardest not to bin food. Or anything else. But that's a whole different story. I still sometimes have nightmares about the giant rubber band ball - not because it was used for anything awful, but just because it. never. stopped. growing.)
Anyway, I did over-order last time so am in exactly the same position as you now with a block of butter (well, a roll, in this case). It is going to be turned into scones and/or shortbread. We also sometimes mash it into boiled potatoes or swede, and cook pancakes in it (though obviously that last one doesn't use up much). The roll I'm planning on using is salted, and a couple of weeks out of date now and it has been refrigerated and sealed that whole time.
There's some advice at www.which.co.uk/news/2020/04/coronavirus-is-it-ever-safe-to-keep-foods-after-their-best-before-and-use-by-dates/ and for a lighter take on it, this US article has a few links to some 2018 science work that was done on whether it's safe or not. There's also a pictorial guide at www.wikihow.com/Test-the-Freshness-of-Butter
Sorry not to give a definitive answer on that one, but just "Well, it depends..."
(I have loved this thread, though, it's one of my recent favourites. Last year we stopped in the Peak District on our way up north and the little village we stayed in had a cheese shop which sold things like Lancashire Bomb cheese. And the most gorgeous walnut cracker things to go with it. We even gave in and finally bought a cheese knife.)