鸿蒙应用示例：工作中常用的日期时间处理方法

import { systemDateTime } from '@kit.BasicServicesKit';
@Entry@Componentstruct Index {  @State formattedTimeNow: string = "";  @State formattedTimeAgo: string = "";  @State timestampSecs: string = "";  @State timestampSecsAlt: string = "";  @State fullDateTime: string = "";  @State nanosecondsTimestamp: string = "";  @State timezoneOffsetHours: string = "";  @State currentDate: string = "";  @State formattedSpecifiedDateTime: string = "";
  formatTimeAgo(dateTime: Date): string {    const now = new Date();    const diff = now.getTime() - dateTime.getTime();    const SECONDS = 1000;    const MINUTES = SECONDS * 60;    const HOURS = MINUTES * 60;    const DAYS = HOURS * 24;
    if (diff < SECONDS) {      return '刚刚';    } else if (diff < MINUTES) {      return '不到一分钟';    } else if (diff < HOURS) {      return Math.round(diff / MINUTES) + '分钟前';    } else if (diff < DAYS) {      return Math.round(diff / HOURS) + '小时前';    } else if (diff < DAYS * 2) {      return '昨天';    } else if (diff < DAYS * 3) {      return '前天';    } else {      return this.formatDate(dateTime);    }  }
  formatDate(dateTime: Date): string {    const year = dateTime.getFullYear();    const month = String(dateTime.getMonth() + 1).padStart(2, '0');    const day = String(dateTime.getDate()).padStart(2, '0');    return `${year}年${month}月${day}日`;  }
  getFullDateTime(): string {    const formatter = new Intl.DateTimeFormat('zh-CN', {      year: 'numeric',      month: '2-digit',      day: '2-digit',      hour: '2-digit',      minute: '2-digit',      second: '2-digit'    });    return formatter.format(new Date());  }
  formatCustomDateTime(dateTime: Date): string {    const formatter = new Intl.DateTimeFormat('zh-CN', {      year: 'numeric',      month: '2-digit',      day: '2-digit'    });    const parts = formatter.formatToParts(dateTime);    let formattedDate = '';    for (const part of parts) {      switch (part.type) {        case 'month':          formattedDate += `${part.value}月`;          break;        case 'day':          formattedDate += `${part.value}日`;          break;        case 'year':          formattedDate = `${part.value}年${formattedDate}`;          break;        default:          break;      }    }    return formattedDate;  }
  getFormattedSpecifiedDateTime(dateTime: Date): string {    return this.formatCustomDateTime(dateTime);  }
  getNanosecondsTimestamp(): void {    const time = systemDateTime.getTime(true);    this.nanosecondsTimestamp = time.toString();  }
  getTimezoneOffsetHours(): void {    try {      const now = new Date();      const offsetMinutes = now.getTimezoneOffset();      const offsetHours = Math.floor(-offsetMinutes / 60);      this.timezoneOffsetHours = offsetHours.toString();    } catch (error) {      console.error('获取时区偏移量失败:', error);      this.timezoneOffsetHours = '未知';    }  }
  getCurrentYearMonthDay(): string {    const date = new Date();    const year = date.getFullYear();    const month = String(date.getMonth() + 1).padStart(2, '0');    const day = String(date.getDate()).padStart(2, '0');    return `${year}年${month}月${day}日`;  }
  build() {    Column({ space: 10 }) {      Button('获取当前时间戳（秒）').onClick(() => {        this.timestampSecs = Math.floor(Date.now() / 1000).toString()        this.timestampSecsAlt = Math.floor(new Date().getTime() / 1000).toString()      })      Text(`当前时间戳（秒）：${this.timestampSecs}`)      Text(`当前时间戳（秒）：${this.timestampSecsAlt}`)
      Button('获取当前时间戳（纳秒）').onClick(() => {        this.getNanosecondsTimestamp();      })      Text(`当前时间戳（纳秒）：${this.nanosecondsTimestamp}`)
      Button('获取时间间隔显示').onClick(() => {        this.formattedTimeNow = this.formatTimeAgo(new Date());        this.formattedTimeAgo = this.formatTimeAgo(new Date('2023-04-01T12:00:00'));      })      Text(`当前时间间隔显示：${this.formattedTimeNow}`)      Text(`指定时间间隔显示：${this.formattedTimeAgo}`)
      Button('获取当前时区偏移量').onClick(() => {        this.getTimezoneOffsetHours();      })
      Text(`当前时区偏移量：${this.timezoneOffsetHours}小时`)
      Button('获取当前年-月-日').onClick(() => {        this.currentDate = this.getCurrentYearMonthDay();      })      Text(`当前年-月-日：${this.currentDate}`)
      Button('获取当前完整时间').onClick(() => {        this.fullDateTime = this.getFullDateTime();      })      Text(`当前完整时间：${this.fullDateTime}`)
      Button('获取指定日期时间').onClick(() => {        this.formattedSpecifiedDateTime = this.getFormattedSpecifiedDateTime(new Date('2024-10-02T09:30:00'));      })      Text(`指定日期时间：${this.formattedSpecifiedDateTime}`)    }    .width('100%')    .height('100%')  }}