I've read through the published book of stories now -- can confirm that in at least two of the stories, it says "now" is "2020" when obviously the original story would have had the date of when it was written (early 1970s, most likely). It doesn't affect the story in any way, and is one of a few minor noticeable edits which possibly make the stories more palatable for the children of today. On the whole, I don't think they touched Terry's language or references all that much (there are many which refer to things which would have been fairly normal in everyday life in the 70s but are somewhat rare or unknown to today's kids).