Issue #21199 has been reported by fitmap (Justin Peal). ---------------------------------------- Bug #21199: Psych.dump and load on Date before 1582-10-15 https://bugs.ruby-lang.org/issues/21199 * Author: fitmap (Justin Peal) * Status: Open * ruby -v: ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x64-mingw-ucrt] * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- The code is: require 'date' require 'psych' date = Date.new(1582, 10, 4) p "date=#{date.inspect}" str = Psych.dump(date, permitted_classes: [Date]) p "str=#{str}" date2 = Psych.load(str, permitted_classes: [Date]) p "date2=#{date2.inspect}" The output is: "date=#<Date: 1582-10-04 ((2299160j,0s,0n),+0s,2299161j)>" "str=--- 1582-10-14\n" "date2=#<Date: 1582-10-14 ((2299160j,0s,0n),+0s,-Infj)>" -- https://bugs.ruby-lang.org/