I was upgrading a Rails 4.1 app from Ruby 2.2.3 to 2.3.1 and got an interesting error; from a debugger session: (byebug) rand(20.minutes) NoMethodError Exception: undefined method `begin' for 1200:Fixnum Ben Sullivan has a nice writeup of some oddities around Rails 4.1's ActiveSupport::Duration and how it uses BasicObject (and David Stostik talks about it more here), so I won't repeat that here. T