看看这个案例:ruby1.9.2p0(2010-08-18修订版29036)[i686-linux]irb(main):006:0>YAML::ENGINE.yamler="psych"=>"psych"irb(main):007:0>'8902-20-13'.to_yamlArgumentError:invaliddatefrom/usr/local/lib/ruby/1.9.1/date.rb:1022:in`new_by_frags'from/usr/local/lib/ruby/1.9.1/date.rb:1046:in`strptime'from/usr/local/lib/