EventMapper/assets/scripts/modules/relative_time.js

// in miliseconds
export const units = {
  year: 24 * 60 * 60 * 1000 * 365,
  month: (24 * 60 * 60 * 1000 * 365) / 12,
  week: 7 * 24 * 60 * 60 * 1000,
  day: 24 * 60 * 60 * 1000,
  hour: 60 * 60 * 1000,
  minute: 60 * 1000,
  second: 1000,
};

export function getRelativeTime(d1, d2, locale) {
  let rtf = new Intl.RelativeTimeFormat(locale, {
    numeric: "auto",
  });

  let elapsed = d1 - d2;

  if (Math.abs(elapsed) >= units.year) {
    return d1.toLocaleDateString(locale, {
      weekday: "long",
      month: "long",
      day: "numeric",
      year: "numeric",
    });
  } else if (Math.abs(elapsed) >= units.day) {
    return d1.toLocaleDateString(locale, {
      weekday: "long",
      month: "long",
      day: "numeric",
    });
  }

  // "Math.abs" accounts for both "past" & "future" scenarios
  for (var u in units)
    if (Math.abs(elapsed) > units[u] || u == "second")
      return rtf.format(Math.round(elapsed / units[u]), u);
}

export function sameDay(d1, d2) {
  return Math.abs(d2.getTime() - d1.getTime()) < units.day;
}

export function DatetoLocaleDynamicString(d1, ref, lang) {
  if (sameDay(d1, ref))
    return d1.toLocaleTimeString(lang, {
      timeStyle: "short",
    });
  else
    return d1.toLocaleDateString(lang, {
      dateStyle: "short",
    });
}