docs: function isYearSeparator() {
    if (yearSeparator !== null) {
      return yearSeparator;
    }
  
    if (!('Intl' in window)) {
      return true;
    }
  
    const options = { day: 'numeric', month: 'short', year: 'numeric' };
    const formatter = new window.Intl.DateTimeFormat(undefined, options);
    const output = formatter.format(new Date(0));
  
    yearSeparator = !!output.match(/\d,/);
    return yearSeparator;
  }