Utility to format dates relatively without having to specify units.

format-relative.js

const { language = 'en-US' } = navigator;

const formatter = new Intl.RelativeTimeFormat(language, {
  numeric: 'auto',
  style: 'long',
});

export function formatRelative(when) {
  const ms = when - Date.now();
  const years = Math.ceil(ms / 31536e6);
  if (years) return formatter.format(years, 'year');
  const months = Math.ceil(ms / 168e6);
  if (months) return formatter.format(months, 'month');
  const days = Math.ceil(ms / 864e5);
  if (days) return formatter.format(days, 'day');
  const hours = Math.ceil(ms / 36e5);
  if (hours) return formatter.format(hours, 'hour');
  const minutes = Math.ceil(ms / 6e4);
  if (minutes) return formatter.format(minutes, 'minute');
  const seconds = Math.ceil(ms / 1e3);
  return formatter.format(seconds, 'second');
}