docs: function time_format(options) {
    if (_.isString(options.time)) {
      /* Translate the string we've been given into a format */
      switch(options.time) {
      case 'days':
      case 'Days':
        return "%d/%m";
      case 'hours':
      case 'Hours':
        return "%H:%M";
      default: /* Presume we've been given a gnuplot-readable time format string */
        return options.time;
      }
    } else { /* Just default to hours */
      return "%H:%M";
    }
  }