[Manishearth]

This is tested in Intl.DateTimeFormat but not in Temporal: you aren't allowed to specify sub-minute offsets within the [timezone] annotation, even if the sub-minute value is zero.

This also covers the different ways of specifying offsets.

[github-actions]

23 new or modified tests were run on 7 engines.

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Test results

Test	Engine262	GraalJS	JavaScriptCore	QuickJS	SpiderMonkey	V8	XS
built-ins/Temporal/Duration/compare/relativeto-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/Duration/prototype/round/relativeto-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/Duration/prototype/total/relativeto-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/Instant/prototype/toString/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/Instant/prototype/toZonedDateTimeISO/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/Now/plainDateISO/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/Now/plainDateTimeISO/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/Now/plainTimeISO/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/Now/zonedDateTimeISO/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/PlainDate/prototype/toZonedDateTime/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/PlainDateTime/prototype/toZonedDateTime/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/compare/argument-propertybag-timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/compare/argument-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/from/argument-propertybag-timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/from/argument-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/prototype/equals/argument-propertybag-timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/prototype/equals/argument-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/prototype/since/argument-propertybag-timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/prototype/since/argument-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/prototype/until/argument-propertybag-timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/prototype/until/argument-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/prototype/withTimeZone/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌
built-ins/Temporal/ZonedDateTime/timezone-string-sub-minute-offset.js	✅	✅	✅	❌	✅	❌	❌

[ptomato]

Makes sense, thanks!