function dayDiff(earlier, later) {
  const utcDayStart = (dt) => dt.toUTC(0, { keepLocalTime: true }).startOf("day").valueOf(),
    ms = utcDayStart(later) - utcDayStart(earlier);
  return Math.floor(Duration.fromMillis(ms).as("days"));
}

function dayDiff(earlier, later) {
  const utcDayStart = (dt) => dt.toUTC(0).startOf("day").valueOf(),
    ms = utcDayStart(later) - utcDayStart(earlier);
  return Math.floor(Duration.fromMillis(ms).as("days"));
}

test("DateTime#diff works when date has a zone object", () => {
  const start = DateTime.fromISO("2022-05-05T23:00", { zone: "UTC" });
  const end = DateTime.fromISO("2022-05-10T00:00", { zone: "Europe/Madrid" });

  const diff = end.diff(start, ["days", "hours", "minutes"]).toObject();
  expect(diff.days).toBe(3);
  expect(diff.hours).toBe(23);
  expect(diff.minutes).toBe(0);
});