estructurar();

function estructurar() {
  //Mes
  let mes = document.createElement("DIV");
  mes.className = "mes";
  document.body.appendChild(mes);
  //Tabla
  let tabla_mes = document.createElement("TABLE");
  tabla_mes.className = "tabla_mes";
  mes.appendChild(tabla_mes);
  //Título
  let titulo = document.createElement("CAPTION");
  titulo.className = "titulo";
  titulo.innerText = "Enero";
  tabla_mes.appendChild(titulo);
}

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.