relativeTime.js

export const timeSinceNow = (timestamp) => {
  const current = new Date()
  const previous = new Date(timestamp * 1000)
  const msPerMinute = 60 * 1000
  const msPerHour = msPerMinute * 60
  const msPerDay = msPerHour * 24
  const msPerMonth = msPerDay * 30
  const msPerYear = msPerDay * 365

  const elapsed = current - previous
  if (elapsed < msPerMinute) return Math.round(elapsed / 1000) + ' seconds ago'
  if (elapsed < msPerHour) return Math.round(elapsed / msPerMinute) + ' minutes ago'
  if (elapsed < msPerDay) return Math.round(elapsed / msPerHour) + ' hours ago'
  if (elapsed < msPerMonth) return Math.round(elapsed / msPerDay) + ' days ago'
  if (elapsed < msPerYear) return Math.round(elapsed / msPerMonth) + ' months ago'
  return Math.round(elapsed / msPerYear) + ' years ago'
}