NodeJS reports incorrect time zone for Brazil

[albertyw]

• Version: v13.0.1
• Platform: Darwin 18.7.0 Darwin Kernel Version 18.7.0: Tue Aug 20 16:57:14 PDT 2019
• Subsystem: N/A

Node is reporting the wrong time zone for Brazil after its cancelled daylight savings change on November 2.

Reproduction:

var process = require('process');
console.log('ICU version: ' + process.versions.icu);

var options = {
    timeZone: "America/Sao_Paulo",
    year: 'numeric', month: 'numeric', day: 'numeric',
    hour: 'numeric', minute: 'numeric', second: 'numeric',
    timeZoneName: 'short'
};

var formatter = new Intl.DateTimeFormat([], options);

var UTCTimeBefore = new Date(new Date().toUTCString());
var UTCTimeAfter = new Date(UTCTimeBefore.getTime() + (7 * 24 * 60 * 60 * 1000));
var UTCTimeAfter = new Date(UTCTimeBefore.getTime() + (30 * 24 * 60 * 60 * 1000));
var localTime = formatter.format(UTCTimeBefore);
console.log('Should be GMT-3')
console.log(localTime);
var localTime = formatter.format(UTCTimeAfter);
console.log('Should also be GMT-3')
console.log(localTime);

Outputs:

ICU version: 64.2
Should be GMT-3
11/1/2019, 7:19:15 PM GMT-3
Should also be GMT-3
12/1/2019, 8:19:15 PM GMT-2

I believe this is because node v13.0.1 depends on ICU version 64.2 which includes tzdata 2019a. However, brazil's updated daylight savings was added in tzdata 2019b, which requires a minimum ICU version of 65.1.

[targos]

Tracking issue for update to ICU 65.1: #29540

[apaprocki]

Time zone data files are updated independently of ICU. You do not need to tie updating time zone data with upgrading ICU, which could have other consequences.

To update the existing ICU 64 .dat file:

• decompress the icudt64l.dat archive
• download the 2019c files from https://github.com/unicode-org/icu-data/tree/master/tzdata/icunew (le little-endian, and be big-endian, depending on platform)
• follow the instructions at http://userguide.icu-project.org/datetime/timezone to patch the .dat file for all four time zone resource files (the resource files must be in the current directory):

  icupkg -a <resourceFile> icutdt64l.dat

• if you want, verify that there is only one of each file in the .dat file using the -l list option
• if you want, verify that after you -x extract the file, the shasum matches what you intended to patch
• compress the icudt64l.dat archive as before

To test the patched file works...

Existing Node v12.13.0 release:

$ node -e 'console.log(Intl.DateTimeFormat("en-US", { dateStyle: "long", timeStyle: "long", timeZone: "America/Sao_Paulo" }).format(Date.UTC(2019, 10, 4, 23)))'
November 4, 2019 at 9:00:00 PM GMT-2

After patching .dat file:

$ node -e 'console.log(Intl.DateTimeFormat("en-US", { dateStyle: "long", timeStyle: "long", timeZone: "America/Sao_Paulo" }).format(Date.UTC(2019, 10, 4, 23)))'
November 4, 2019 at 8:00:00 PM GMT-3

If it helps, the shasum of the v12.13.0 release and patched files:
Release: 2b681d53f193f714db86b038176da6866f8d5afd icudt64l.dat
Patched: 7317c1d424812d9ef1ed318e70db7ed27b93853c icudt64l.dat

[MylesBorins]

/cc @srl295

[srl295]

@apaprocki would you like to make a PR to update tools/icu/ with a readme about how to do this? Good instructions. I would add that you can have the updated tz data outside of node.js, without recompiling, i will have to add detailed instructions for that.

additionally, process.versions.tz will return the tz version such as 2019b