frigate/web-new/src/lib/formatTimeAgo.ts

const formatter = new Intl.RelativeTimeFormat(undefined, {
    numeric: "always",
  })

  const DIVISIONS: { amount: number; name: Intl.RelativeTimeFormatUnit }[] = [
    { amount: 60, name: "seconds" },
    { amount: 60, name: "minutes" },
    { amount: 24, name: "hours" },
    { amount: 7, name: "days" },
    { amount: 4.34524, name: "weeks" },
    { amount: 12, name: "months" },
    { amount: Number.POSITIVE_INFINITY, name: "years" },
  ]

  export function formatTimeAgo(date: Date) {
    let duration = (date.getTime() - new Date().getTime()) / 1000

    for (let i = 0; i < DIVISIONS.length; i++) {
      const division = DIVISIONS[i]
      if (Math.abs(duration) < division.amount) {
        return formatter.format(Math.round(duration), division.name)
      }
      duration /= division.amount
    }
  }