message: docs(Calendar): update demo
diff: <van-cell
  is-link
  :title="$t('selectSingleDate')"
  - :value="formatDate(date.selectSingleDate)"
  + :value="formatFullDate(date.selectSingleDate)"
  @click="toggle('selectSingleDate', true)"
  />
  @@ -78,15 +78,20 @@ export default {
  formatDate(date) {
  if (date) {
  - return `${date.getFullYear()}/${date.getMonth() + 1}/${date.getDate()}`;
  + return `${date.getMonth() + 1}/${date.getDate()}`;
  + }
  + },
  +
  + formatFullDate(date) {
  + if (date) {
  + return `${date.getFullYear()}/${this.formatDate(date)}`;
  }
  },
  formatDateRange(dateRange) {
  if (dateRange.length) {
  - return `${this.formatDate(dateRange[0])} - ${this.formatDate(
  - dateRange[1]
  - )}`;
  + const [start, end] = dateRange;
  + return `${this.formatDate(start)} - ${this.formatDate(end)}`;
  }
  }
  }
  