How can I make the array of numbers in the calendar start from the first position?

Question

JavaScript

Good afternoon, tell me please. I'm trying to write a calendar and I'm having a problem that all the numbers of the months start on Tuesday, please help me to make them start on Monday. That is, move all numbers one position back.
This is what the calendar looks like now:

Calendar code:

<template>
  <div class="all">
    <div class="overflow-div">
      <div class="pagination">
        <div @click="prevPage" class="btn-left"><</div> 
        <p>{{ nameOfOneMonth }} {{ year }}</p>
        <div @click="nextPage" class="btn-right">></div> 
      </div>

        <div class="d_nameOfDays">
          <li v-for="day in nameOfDays" class="nameOfDays">{{ day }}</li>
        </div>
        <transition :name="nameOfClass" >
          <div :key="currentPage" class="fade_wrapper">
            <div v-for="(week, i) in getCalendar" class="d_day">
            <li v-for="day in week" class="li_day">
            <div class="day">{{ day }}</div>
              </li>
            </div>
          </div>
        </transition>
    </div>
  </div> 
</template>

<script>
  import json from './Calendar_data.json'
export default {
  data(){
    return{
      currentPage: 0,
      namesOfMonths: ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'],
      nameOfOneMonth: '',
      nameOfDays: ['Пн', 'Вт', 'Ср', 'Чт', 'Пт', 'Сб', 'Вс'],
      date: new Date(),
      isActive: true,
      year: '',
      nameOfClass: '',
      eventsData: json
    }
  },
  computed: {
    getCalendar(){
      return this.buildCalendar();
    }
  },
  mounted(){
    this.year = this.date.getFullYear();
    this.currentPage = this.date.getMonth();
    this.nameOfOneMonth = this.namesOfMonths[this.currentPage];
  },
  methods: {
    prevPage(){
      if (this.currentPage === 0) {
        this.currentPage = 12;
        this.year--;
      }
      this.nameOfClass = 'prev';
      this.currentPage--;
      this.nameOfOneMonth = this.namesOfMonths[this.currentPage];
    },
    nextPage(){
      if (this.currentPage === 11) {
        this.currentPage = -1;
        this.year++;
      }
      this.nameOfClass = 'next';
      this.currentPage++;
      this.nameOfOneMonth = this.namesOfMonths[this.currentPage];
    },
    getYear(){
      this.year = this.date.getFullYear();
    },
    getLastDayOfMonth(month) { 
      let dateDaysInMonth = new Date(this.year, month + 1, 0);
      return dateDaysInMonth.getDate();
    },
    buildCalendar(){
      let arrOfEvents = this.eventsData.events;
      let massOfMonth = [];
      for (let months = 0; months < 12; months++){
        massOfMonth.push(months);
        massOfMonth[months] = [];
        for ( let daysInMonth = 1; daysInMonth <= this.getLastDayOfMonth(months); daysInMonth++){
          massOfMonth[months][daysInMonth] = [];
          massOfMonth[months][daysInMonth].push(daysInMonth)
          for(let z = 0; z < arrOfEvents.length; z++){
            let d = arrOfEvents[z].starts_at;
            let v = new Date(d);
            let memo = arrOfEvents[z].memo;
            if(daysInMonth == v.getDate()){
              massOfMonth[months][daysInMonth].push(memo)
            };
          }
        }
      var longArray = massOfMonth[this.currentPage];
      var size = 7;

      var newArray = new Array(Math.ceil(longArray.length / size)).fill("")
          .map(function() { 
            return this.splice(0, size) 
          }, longArray.slice());

        return newArray;
    }
  }
};
</script>

Answer 1

With a quick glance, I can suggest replacing let daysInMonth = 1 with 0