We store a field of variable types. It can be an array of String, Date or Time in any quantity and combinations.

 ruby
class Artwork
  include Mongoid::Document

  field :dates, type: Array
end

Mongoid 2.x

 ruby
Artwork.new({ dates: [ Date.parse("3/5/2011") ]}).dates.first.class
 => Date

Mongoid 3.x

 ruby
Artwork.new({ dates: [ Date.parse("3/5/2011") ]}).dates.first.class
 => Time 

Is this by design or a bug? I would expect that storing a date returns a date. Is there an easy way to get old behavior back?