def post_date_url(post, root_page):
    """Generates post url that includes the first_published_at date."""
    date = post.first_published_at
    url = root_page.url + root_page.specific.reverse_subpage(
        'post_by_date_slug',
        args=(
            date.year,
            date.strftime('%b').lower(),
            date.strftime('%d'),
            post.slug
        )     
    )
    return url