import {
  addDays,
  addMonths,
  eachDayOfInterval,
  eachWeekOfInterval,
  startOfMonth,
} from 'date-fns'

const startOfMonthDate = startOfMonth(new Date())
const matrix = eachWeekOfInterval({
  start: startOfMonthDate,
  end: addMonths(startOfMonthDate, 1),
}).map((weekDay) => {
  const startDate = new Date(weekDay)

  return eachDayOfInterval({
    start: startDate,
    end: addDays(startDate, 6),
  })
})

• matrix 구현
  • bclinkinbeard/calendar-matrix
  • Calendar Matrix (date-fns, ES6)
• 튜토리얼
  • How to Make a Monthly Calendar With Real Data | CSS-Tricks
  • Let’s Make a Vue-Powered Monthly Calendar | CSS-Tricks

dayjs로 특정 날짜가 포함된 주의 모든 날짜 가져오기

import dayjs from 'dayjs'
import isoWeek from 'dayjs/plugin/isoWeek'
dayjs.extend(isoWeek)

// startOf('week') → 일요일 시작
// startOf('isoWeek') → 월요일 시작 (캘린더 UI에 주로 사용)
function getWeekDays(date, iso = true) {
  const start = dayjs(date).startOf(iso ? 'isoWeek' : 'week')
  return Array.from({ length: 7 }, (_, i) =>
    start.add(i, 'day').format('YYYY-MM-DD')
  )
}

getWeekDays('2025-10-28') // ['2025-10-27', ..., '2025-11-02']