18F/calc

<form method="post"
      action="{% url 'styleguide:date' %}">
  {% csrf_token %}

  {% with form=date_form %}
    <fieldset>
      <legend>{{ form.date.label }}</legend>
      {{ form.date.errors }}
      {{ form.date }}
    </fieldset>
  {% endwith %}

  <button type="submit" class="usa-button usa-button-primary">Submit</button>
</form>