reproduces issue 3965 config.time_zone and datetime update

gistfile1.txt

gem 'rails', '3.2.1'
require 'active_record'

# Print out what version we're running
puts "Active Record #{ActiveRecord::VERSION::STRING}"

ActiveRecord::Base.time_zone_aware_attributes = true
ActiveRecord::Base.default_timezone = :utc
Time.zone = 'Amsterdam'

# Connect to an in-memory sqlite3 database
ActiveRecord::Base.establish_connection(
  :adapter  => 'sqlite3',
  :database => ':memory:'
)

# Create schema
ActiveRecord::Schema.define do
  create_table :foos, :force => true do |t|
    t.datetime :bar
  end
end

# Create the a model
class Foo < ActiveRecord::Base
end

# reproduce bug
foo = Foo.create(:bar => "2012-02-20 10:00:00")

foo.bar = "2012-02-20 09:00:00"
# expected: true
puts foo.bar_changed?

foo.bar = "2012-02-20 10:00:00"
#  expected: false
puts foo.bar_changed?