function Pandoc(doc)
  local heading

  for _, block in ipairs(doc.blocks) do
    if block.t == "Header" and block.level == 1 then
      heading = block
    elseif heading and block.t == "Para" then
      local date = pandoc.utils.stringify(block.content)
      table.insert(heading.content, pandoc.RawInline(
        "html", '<span class="article-date">' .. date .. "</span>"
      ))
      heading = nil
    else
      heading = nil
    end
  end

  return doc
end