message: [Improvement] DatetimePicker: refactor getMonthEndDay function
diff: @@ -256,21 +256,7 @@ export default create({
  },
  getMonthEndDay(year, month) {
  - if (this.isShortMonth(month)) {
  - return 30;
  - } else if (month === 2) {
  - return this.isLeapYear(year) ? 29 : 28;
  - } else {
  - return 31;
  - }
  - },
  -
  - isLeapYear(year) {
  - return (year % 4 === 0 && year % 100 !== 0) || (year % 400 === 0);
  - },
  -
  - isShortMonth(month) {
  - return [4, 6, 9, 11].indexOf(month) > -1;
  + return 32 - new Date(year, month - 1, 32).getDate();
  },
  onConfirm() {
  