Rails 4 and Ruby 2 date format validation

gistfile1.rb

# Model

# Working in Rails 3 with Ruby 1.9.3 - always returning false in Rails 4 with Ruby 2
with_options :if => :condition? do |co|
  co.validates :date_birth, :format => {:with => /[0-3]{1}[0-9]{1}\/[0-1]{1}[0-9]{1}\/[1-2]{1}[0-9]{3}/, :message => "invalid"}
  # I also tried below and many others regex
  #co.validates :date_birth, :format => {:with => /[1-2]{1}[0-9]{3}\-[0-1]{1}[0-9]{1}\-[0-3]{1}[0-9]{1}/, :message => "invalid"}
end

# Workaround to work in Rails 4 with Ruby 2
with_options :if => :condition? do |co|
  co.validate  :valid_date_birth
end

private
  def valid_date_birth
    if self.date_birth.blank? || !(/[1-2]{1}[0-9]{3}\-[0-1]{1}[0-9]{1}\-[0-3]{1}[0-9]{1}/.match(self.date_birth.to_s))
      errors[:date_birth] = 'invalid'
    end
  end