Some common operations I perform with Unix time

unixHelpers.js

const SECONDS_IN_A_DAY = 86400

let sts = 1629072000
let ets = 0

const unixMidnight = time => {
  return time - (time % SECONDS_IN_A_DAY)
}

const addDay = time => {
  return time + SECONDS_IN_A_DAY
}

const getNextDays = (time, nextDays) => {
  const days = []
  
  for (let i = 0; i < nextDays; i++) {
    days.push(time)
    time = addDay(time)
  }

  return days
}