America/Asuncion still on UTC-4

[aza547]

Version

20.19.0

Platform

Microsoft Windows NT 10.0.26100.0 x64

Subsystem

No response

What steps will reproduce the bug?

• Set to America/Asuncion timezone.
• Access the Date class and get wrong times.

Some code to log it out I've been using:

const tz = Intl.DateTimeFormat().resolvedOptions().timeZone;
const tzOffset = new Date().getTimezoneOffset() * -1; // Offset is wrong direction so flip it.
const tzOffsetStr = `UTC${tzOffset >= 0 ? '+' : ''}${tzOffset / 60}`;

console.info('[Main] Node version', process.versions.node);
console.info('[Main] In timezone:', tz, tzOffsetStr);

How often does it reproduce? Is there a required condition?

Always when set to America/Asuncion timezone.

What is the expected behavior? Why is that the expected behavior?

America/Asuncion timezone should be UTC-3.

What do you see instead?

In my electron app (electron 34.5.0, using Node 20.19.0):

[2025-04-06 17:30:10.234] [info]  [Main] Node version 20.19.0
[2025-04-06 17:30:10.236] [info]  [Main] In timezone: America/Asuncion UTC-4

Additional information

Looks like this was addressed by: #56876

Possible (probable?) I'm doing something stupid but seems like it may not have taken effect and there is a problem with the timezone data.

[avivkeller]

Node.js gets it's timezone data from ICU, and it not directly responsible for the timezones presented.

[LiviaMedeiros]

In the main branch with built-in full-icu, this is already resolved:

[Main] Node version 24.0.0-pre
[Main] In timezone: America/Asuncion UTC-3

> console.log(process.versions.icu);
77.1

The PR that fixes this is #57455 which is not included in release yet.

An alternative solution is building Node.js locally with --with-intl=system-icu flag and providing system-wide ICU with newer version.

Closing this as resolved, feel free to reopen if this doesn't look right.

[aza547]

Hmm thanks - I do seem to have a different ICU version (74.2).

I saw that #57685 was in the Node 20.19.0 tag, which describes the time zone change in question, guess the PR you linked is also required.

Anyway - thanks for the response. I'll sit tight till there is a new release I can pick up.

[richardlau]

20.19.0 from https://nodejs.org/dist/v20.19.0/node-v20.19.0-win-x64.zip appears to give the expected result for me:

C:\Users\rlau>node --version
v20.19.0

C:\Users\rlau>type test.js
const tz = Intl.DateTimeFormat().resolvedOptions().timeZone;
const tzOffset = new Date().getTimezoneOffset() * -1; // Offset is wrong direction so flip it.
const tzOffsetStr = `UTC${tzOffset >= 0 ? '+' : ''}${tzOffset / 60}`;

console.info('[Main] Node version', process.versions.node);
console.info('[Main] In timezone:', tz, tzOffsetStr);
C:\Users\rlau>set TZ=America/Asuncion

C:\Users\rlau>node test.js
[Main] Node version 20.19.0
[Main] In timezone: America/Asuncion UTC-3

C:\Users\rlau>node -p process.versions
{
  node: '20.19.0',
  acorn: '8.14.0',
  ada: '2.9.2',
  ares: '1.34.4',
  brotli: '1.1.0',
  cjs_module_lexer: '1.4.1',
  cldr: '46.0',
  icu: '76.1',
  llhttp: '8.1.2',
  modules: '115',
  napi: '9',
  nghttp2: '1.61.0',
  nghttp3: '0.7.0',
  ngtcp2: '1.1.0',
  openssl: '3.0.15+quic',
  simdutf: '6.0.3',
  tz: '2025a',
  undici: '6.21.1',
  unicode: '16.0',
  uv: '1.46.0',
  uvwasi: '0.0.21',
  v8: '11.3.244.8-node.26',
  zlib: '1.3.0.1-motley-82a5fec'
}

C:\Users\rlau>

[richardlau]

Hmm thanks - I do seem to have a different ICU version (74.2).

@aza547 You'll probably need to check with Electron which ICU they're using. If they're not using the one bundled in Node.js then they'll need to patch the timezones independently.