1 files changed, 11 insertions, 1 deletions
diff --git a/activesupport/lib/active_support/json/backends/yaml.rb b/activesupport/lib/active_support/json/backends/yaml.rb
index b1dd2a8107..077eda548a 100644
--- a/activesupport/lib/active_support/json/backends/yaml.rb
+++ b/activesupport/lib/active_support/json/backends/yaml.rb
@@ -36,7 +36,7 @@ module ActiveSupport
                   quoting = char
                   pos = scanner.pos
                 elsif quoting == char
-                  if json[pos..scanner.pos-2] =~ DATE_REGEX
+                  if valid_date?(json[pos..scanner.pos-2])
                     # found a date, track the exact positions of the quotes so we can
                     # overwrite them with spaces later.
                     times << pos
@@ -94,6 +94,16 @@ module ActiveSupport
               output
             end
           end
+
+        private
+          def valid_date?(date_string)
+            begin
+              date_string =~ DATE_REGEX && DateTime.parse(date_string)
+            rescue ArgumentError
+              false
+            end
+          end
+
       end
     end
   end