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