Currently I have a function to check if the birthyear is correct:

```
  validates :birth_year, presence: true,
            format: {with: /(19|20)\d{2}/i }

```

I also have a function that checks if the date is correct:

```
  validate :birth_year_format

  private

  def birth_year_format
    errors.add(:birth_year, "should be a four-digit year") unless (1900..Date.today.year).include?(birth_year.to_i)
  end

```

Is it possible to combine the bottom method into the `validates` at the top instead of the two validates I have now?