function getSeason () {
  var today       = new Date();
  var today_day   = today.getDate();
  var today_month = today.getMonth() + 1;

  switch (today_month) {
    case 1: case 2:
      return "winter";

    case 3:
      return (today_day < 21) ? "winter" : "spring";

    case 4: case 5:
      return "spring";

    case 6:
      return (today_day < 21) ? "spring" : "summer";

    case 7: case 8:
      return "summer";

    case 9:
      return (today_day < 23) ? "summer" : "autumn";

    case 10: case 11:
      return "autumn";

    case 12:
      return (today_day < 21) ? "autumn" : "winter";
  }
}