May I refer to a particularly well written list of inconsistencies on the Tolkien Gateway here. Both inconsistencies mentioned in this topic are included. I remember some of these disappeared after a number of corrections were made in the “50th Anniversary Edition” so it really depends on which version you’re studying; I refer to the Tolkien Gateway here. You started an interesting topic, Azrubêl. I happen to have both a 1994 hardcopy edition and a 2004 electronic edition so I made a quick check of the example given of Samwise Gamgee’s modified birthdate (from 2983 to 2980) and indeed: I could notice that the correction was made in the later version!