1.md

index.html

let data = {
  closeText: '閉じる',	prevText: '<前', nextText: '次>',
  currentText: '今日', weekHeader: '週', dateFormat: 'yy/mm/dd',
  firstDay: 0, isRTL: false, showMonthAfterYear: true, yearSuffix: '年',
  monthNames: [], monthNamesShort: [], dayNames: [],
  dayNamesShort: [], dayNamesMin: []
};
// 日付の作成（1〜12月）
for (let i = 1; i <= 12; i++) {
  data.monthNames.push(`${i}月`);
  data.monthNamesShort.push(`${i}月`);
}

// 曜日の作成（日〜土曜日）
let weekdays = ['日','月','火','水','木','金','土'];
for (let index in weekdays) {
  data.dayNames.push(`${weekdays[index]}曜日`);
  data.dayNamesShort.push(weekdays[index]);
  data.dayNamesMin.push(weekdays[index]);
}

$.datepicker.regional['ja'] = data;
$.datepicker.setDefaults($.datepicker.regional['ja']);