export const formatRelativeTime = (date: Date, base = new Date()) => {
  const diffSec = Math.round((date.getTime() - base.getTime()) / 1000);
  const rtf = new Intl.RelativeTimeFormat('en', { numeric: 'auto' });
  const divisions: [number, Intl.RelativeTimeFormatUnit][] = [
    [60, 'second'],
    [60, 'minute'],
    [24, 'hour'],
    [7, 'day'],
    [4.34524, 'week'],
    [12, 'month'],
    [Number.POSITIVE_INFINITY, 'year'],
  ];
  let unit: Intl.RelativeTimeFormatUnit = 'second';
  let value = diffSec;
  for (const [amount, u] of divisions) {
    if (Math.abs(value) < amount) {
      unit = u;
      break;
    }
    value /= amount;
  }
  return rtf.format(Math.round(value), unit);
};

// Usage
const pastDate = new Date(Date.now() - 2 * 24 * 60 * 60 * 1000);
formatRelativeTime(pastDate); // "2 days ago"

const future = new Date(Date.now() + 3600000);
formatRelativeTime(future);   // "in 1 hour"