require 'mongoid'

Mongoid.configure do |config|
  config.master = Mongo::Connection.new.db("orred_dates")
end

class Rockstar
  include Mongoid::Document

  has_many :gigs do
    def find_future
      where(time: {"$gt" => DateTime.now})
    end
    def find_future_or_now
      where(
        "$or" => [
          {time: {"$gt" => DateTime.now}},
          {right_now: true}
        ]
      )
    end
    def find_future_or_now_with_time
      where(
        "$or" => [
          {time: {"$gt" => Time.now}},
          {right_now: true}
        ]
      )
    end
  end

end

class Gig
  include Mongoid::Document

  belongs_to :rockstar

  field :time, type: DateTime
  field :right_now, type: Boolean, default: false
end

rockstar = Rockstar.new

rockstar.gigs.build(time: DateTime.parse("May 25, 2012")).save
rockstar.gigs.build(right_now: true).save
rockstar.gigs.build(time: DateTime.parse("May 25, 1965")).save
rockstar.save
rockstar.reload

puts rockstar.gigs.find_future          # works fine
puts rockstar.gigs.find_future_or_now_with_time  #also works
puts rockstar.gigs.find_future_or_now   # error

/home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/bson-1.5.2/lib/bson/bson_c.rb:24:in `serialize': DateTime is not currently supported; use a UTC Time instance instead. (BSON::InvalidDocument)
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/bson-1.5.2/lib/bson/bson_c.rb:24:in `serialize'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongo-1.5.2/lib/mongo/cursor.rb:602:in `construct_query_message'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongo-1.5.2/lib/mongo/cursor.rb:465:in `send_initial_query'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongo-1.5.2/lib/mongo/cursor.rb:458:in `refresh'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongo-1.5.2/lib/mongo/cursor.rb:128:in `next'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongo-1.5.2/lib/mongo/cursor.rb:290:in `each'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongoid-2.4.0/lib/mongoid/cursor.rb:48:in `each'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongoid-2.4.0/lib/mongoid/contexts/mongo.rb:242:in `iterate'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongoid-2.4.0/lib/mongoid/criteria.rb:145:in `block in each'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongoid-2.4.0/lib/mongoid/criteria.rb:145:in `tap'
	from /home/isaac/.rvm/gems/ruby-1.9.2-p290/gems/mongoid-2.4.0/lib/mongoid/criteria.rb:145:in `each'
	from mongoid_or_datetime.rb:44:in `to_a'
	from mongoid_or_datetime.rb:44:in `puts'
	from mongoid_or_datetime.rb:44:in `puts'
	from mongoid_or_datetime.rb:44:in `<main>'

db.gigs.find({
  $or: [
    {right_now: true},
    {time : {$gt : ISODate("2012-01-10T04:00:00Z")}}
  ]
})