hasSame order matters / timezones are not working with hasSame

I noticed that when I compared two DateTime objects with hasSame the ordering of the objects returned different results. It seems to only happen when at least one of the objects has a timezone defined.

I managed to reproduce it, let the code speak for itself:

// With zones
const first = DateTime.fromISO("2019-10-02T07:24:04.339+03:00", {
  zone: "Europe/Helsinki"
});
const second = DateTime.fromISO("2019-10-02T00:00:00.000-05:00", {
  zone: "America/Chicago"
});

console.log(first.hasSame(second, "day")); // true
console.log(second.hasSame(first, "day")); // false
console.log(first.toISO()); // 2019-10-02T07:24:04.339+03:00
console.log(second.toISO()); // 2019-10-02T00:00:00.000-05:00

// No zones
const third = DateTime.fromISO("2019-10-02T07:24:04.339+03:00");
const fourth = DateTime.fromISO("2019-10-02T00:00:00.000-05:00");

console.log(third.hasSame(fourth, "day")); // true
console.log(fourth.hasSame(third, "day")); // true
console.log(first.toISO()); // 2019-10-02T07:24:04.339+03:00
console.log(second.toISO()); // 2019-10-02T08:00:00.000+03:00

[icambron]

It could be! I just need a PR.

[sebastianvoss]

We recently got bitten by this in the context of daylight saving. We were filtering a list of items by item.date.hasSame(today, 'day'). We changed the filter condition to item.date.toISODate() === today.toISODate() to avoid the problem for now. But it would be great if this could be somehow improved.