time_validator.rb

class TimeValidator < ActiveModel::EachValidator
  def validate_each(record, attribute, value)
    flg = true
    if de = options[:before]
      de = Time.now if de == :now
      flg &&= value <= de
    end
    if de = options[:after]
      de = Time.now if de == :now
      flg &&= de <= value
    end
    record.errors.add(attribute, options[:message] || :invalid) unless flg
  end
end