JSTests/test262/test/built-ins/Temporal/Instant/prototype/toString/timezone-offset.js

// Copyright (C) 2021 Igalia, S.L. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.

/*---
esid: sec-temporal.instant.prototype.tostring
description: The time zone offset part of the string serialization
features: [BigInt, Temporal]
---*/

const instant = new Temporal.Instant(0n);

function test(timeZoneIdentifier, expected, description) {
  const timeZone = new Temporal.TimeZone(timeZoneIdentifier);
  assert.sameValue(instant.toString({ timeZone }), expected, description);
}

test("UTC", "1970-01-01T00:00:00+00:00", "offset of UTC is +00:00");
test("+01:00", "1970-01-01T01:00:00+01:00", "positive offset");
test("-05:00", "1969-12-31T19:00:00-05:00", "negative offset");
test("+00:44:59.123456789", "1970-01-01T00:44:59.123456789+00:45", "sub-minute offset");
test("-00:00:10.987654321", "1969-12-31T23:59:49.012345679+00:00", "sub-minute offset that rounds to zero");