Code to experiment with clock drift in MacOS

index.mjs

// Inspired by https://blog.insiderattack.net/how-not-to-measure-time-in-programming-11089d546180
import { execSync } from 'node:child_process'
import { setTimeout } from 'node:timers/promises'
import { performance } from 'node:perf_hooks'

function adiantarTempo () {
  const toTwoDigits = (num) => num.toString().padStart(2, "0")
  const now = new Date()
  const month = toTwoDigits(now.getMonth() + 1)
  const date = toTwoDigits(now.getDate())
  const hours = toTwoDigits(now.getHours())
  const fakeMinutes = toTwoDigits(now.getMinutes() + 1)
  const year = now.getFullYear().toString().substring(2, 4)

  // set fake time
  execSync(`date -u ${month}${date}${hours}${fakeMinutes}${year}`)
}

function correcaoNTP () {
  const output = execSync(`sntp -sS time.apple.com`)
  console.log(`Tempo corrigido: ${output}`)
}

const esperar2Segundos = () => setTimeout(2000)

// ------- Experimento 1: Relógios normais
{
  adiantarTempo()
  const timeNow = Date.now()

  setImmediate(() => correcaoNTP())

  await esperar2Segundos()

  const endTime = Date.now()
  const duration = endTime - timeNow
  console.log(`Duração\t: ${duration}ms`)
}

// ------- Experimento 2: Relógios monotonicos
{
  adiantarTempo()
  const timeNow = performance.now()

  setImmediate(() => correcaoNTP())

  await esperar2Segundos()

  const endTime = performance.now()
  const duration = endTime - timeNow
  console.log(`Duração\t: ${duration}ms`)
}