時刻を任意のフォーマットで扱う
% irb irb(main):001:0> date = Time.now => Wed Apr 09 17:46:56 +0900 2008 irb(main):002:0> p date.strftime("%Y-%m-%d %H:%M:%S") "2008-04-09 17:46:56" => nil irb(main):003:0>
% irb irb(main):001:0> date = Time.now => Wed Apr 09 17:46:56 +0900 2008 irb(main):002:0> p date.strftime("%Y-%m-%d %H:%M:%S") "2008-04-09 17:46:56" => nil irb(main):003:0>