数字だけマッチするならRubyになっちゃうけどとりゃ
ruby -pe '$_.gsub!(/(\d{4,4})-(\d\d)-(\d\d)-/, "\\1\\2\\3_")'
Mastodon is the best way to keep up with what's happening.
Follow anyone across the fediverse and see it all in chronological order. No algorithms, ads, or clickbait in sight.