Vue中

data() {
    return {
      /*当前日期时间*/
      nowYear: '',
      nowMonth: '',
      nowDate: '',
      nowDay: '',
      nowHours: '',
      nowMinutes: '',
      nowSeconds: '',
      turnoverTime: ''
    };
  },

获取当前日期时间

// 获取当前日期时间
    getNowTime() {
      this.nowYear = new Date().getFullYear();
      this.nowMonth = new Date().getMonth()+1;
      this.nowDate = new Date().getDate();
      this.nowDay = new Date().getDay();
      this.nowHours = new Date().getHours();
      this.nowMinutes = new Date().getMinutes()<10 ? '0'+new Date().getMinutes() : new Date().getMinutes();
      this.nowSeconds = new Date().getSeconds()<10 ? '0'+new Date().getSeconds() : new Date().getSeconds();
      this.turnoverTime = this.nowYear+'年'+this.nowMonth+'月'+this.nowDate+'日'+' '+this.nowHours+':'+this.nowMinutes+':'+this.nowSeconds;
    },

获取上周日期

      let thisWeekStart; //本周周一的时间
        if (this.nowDay === 0) {  //周天的情况；
          thisWeekStart = (new Date(this.nowYear + '-' + this.nowMonth + '-' + this.nowDate)).getTime() - ((this.nowDay) + 6) * 86400000;
        } else {
          thisWeekStart = (new Date(this.nowYear + '-' + this.nowMonth + '-' + this.nowDate)).getTime() - ((this.nowDay) - 1) * 86400000;
        }
        //获得上周时间
        var prevWeekStart = thisWeekStart - 7 * 86400000;//上周周一的时间
        var prevWeekEnd = thisWeekStart - 1 * 86400000;//上周周日的时间
        let sTime = this.formatDate(new Date(prevWeekStart)); //开始时间
        let eTime = this.formatDate(new Date(prevWeekEnd));   //结束时间

获取上月日期

var prevCurrentYear = 0, prevCurrentMonth = 0;
        if (this.nowMonth === 1) {
          prevCurrentYear = this.nowYear - 1;
          prevCurrentMonth = 12;
        } else {
          prevCurrentYear = this.nowYear;
          prevCurrentMonth = this.nowMonth - 2;
        }
        //获得上月时间
        var prevmonthLastday = (new Date(this.nowYear, this.nowMonth-1, 1)).getTime() - 86400000;
        let sTime = this.formatDate(new Date(prevCurrentYear, prevCurrentMonth, 1));  //开始时间
        let eTime = this.formatDate(new Date(prevmonthLastday));   //结束时间

获取昨天日期

let date1 = new Date();
let date2 = new Date(date1);
date2.setDate(date1.getDate() - 1);
`${date2.getFullYear()}-${date2.getMonth() + 1<10?`0${date2.getMonth() + 1}`:date2.getMonth() + 1}-${date2.getDate()}`;

获取30天前日期

let date1 = new Date();
let date2 = new Date(date1);
date2.setDate(date1.getDate() - 30);
`${date2.getFullYear()}-${date2.getMonth() + 1<10?`0${date2.getMonth() + 1}`:date2.getMonth() + 1}-${date2.getDate()}`;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

/**
* 根据指定日期获取上月日期
* @param date
* @return
*/
private static Date getLastDate(Date date) {
	Calendar cal = Calendar.getInstance();
	cal.setTime(date);
	cal.add(Calendar.MONTH, -1);
	return cal.getTime();
}

public static void main(String[] args) {
	SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
	Date date;
	try {
		date = sdf.parse("2021-01-09");  //指定日期
		System.out.println("本月：" + sdf.format(date));
		System.out.println("上月" + sdf.format(getLastDate(date)));
	} catch (ParseException e) {
		e.printStackTrace();
	}				
		
}

运行结果：
本月：2021-01-09
上月：2020-12-09

获取如 2020-6-11 到 2020-5-11 排除大小月 本月是大月上月小月为30

    // 获取上月日期
    getPrevDate(date) {
      var arr = date.split('-');
      // 获取当前日期的年份
      var year = arr[0];
      // 获取当前日期的月份
      var month = arr[1];
      var day = arr[2];
      var prevYear = year;
      var prevMonth = parseInt(month) - 1;
      if (prevMonth === 0) {
        // 如果是1月份，则取上一年的12月份
        prevYear = parseInt(prevYear) - 1;
        prevMonth = 12;
      }
      var prevDay = day;
      // 如果原来日期大于上一月的日期，则取当月的最大日期。比如3月的30日，在2月中没有30
      var days2 = new Date(prevYear, prevMonth, 0).getDate();
      if (prevDay > days2) prevDay = days2;
      var prevDate = prevYear + '-' + prevMonth + '-' + prevDay;
      return prevDate;
    }