formatInTimeZone displaying wrong value for 'zzz' in different locales

[jb-]

Using v3.2.0 in React Native project (only tested with iOS).
Tried 2 different timezone in 2 different locales;

1. For Europe/Berlin, enGB works fine but enUS doesn't.

formatInTimeZone(new Date(), 'Europe/Berlin', 'zzz', { locale: enGB }) // ✅ 'CET' (or 'CEST' depending on the date value)
formatInTimeZone(new Date(), 'Europe/Berlin', 'zzz', { locale: enUS }) // ❌ 'GMT' ('CET' or 'CEST' expected)

2. For Pacific/Honolulu, enUS works fine but enGB doesn't.

formatInTimeZone(new Date(), 'Pacific/Honolulu', 'zzz', { locale: enUS }) // ✅ 'HST'
formatInTimeZone(new Date(), 'Pacific/Honolulu', 'zzz', { locale: enGB }) // ❌ 'GMT' ('HST' expected)

[kueda]

I'm seeing this too and I think it might be a bug in Hermes and possibly beyond the scope of this library.

In Firefox 134.0.2 (Chrome seems to behave the same way)

Intl.DateTimeFormat( "en-US", { timeZone: "Pacific/Honolulu", timeZoneName: "short" } ).formatToParts( new Date( ) ).find( p => p.type === "timeZoneName" ).value
// HST
Intl.DateTimeFormat( "en-GB", { timeZone: "Pacific/Honolulu", timeZoneName: "short" } ).formatToParts( new Date( ) ).find( p => p.type === "timeZoneName" ).value 
// GMT-10

In React Native 0.73.7 (and 0.77.0), iOS 18 and iOS 17

Intl.DateTimeFormat( "en-US", { timeZone: "Pacific/Honolulu", timeZoneName: "short" } ).formatToParts( new Date( ) ).find( p => p.type === "timeZoneName" ).value 
// ✅ HST
Intl.DateTimeFormat( "en-GB", { timeZone: "Pacific/Honolulu", timeZoneName: "short" } ).formatToParts( new Date( ) ).find( p => p.type === "timeZoneName" ).value
// ❌ GMT (offset not included)

In React Native 0.73.7 (and 0.77.0), Android 14

Intl.DateTimeFormat( "en-US", { timeZone: "Pacific/Honolulu", timeZoneName: "short" } ).formatToParts( new Date( ) ).find( p => p.type === "timeZoneName" ).value 
// ✅ HST
Intl.DateTimeFormat( "en-GB", { timeZone: "Pacific/Honolulu", timeZoneName: "short" } ).formatToParts( new Date( ) ).find( p => p.type === "timeZoneName" ).value
// ✅ GMT-10 (I would have hoped for HST but at least this matches a browser)