Date.toLocaleString uses "at" instead of "," with dateStyle: "medium"

[bconnorwhite]

What version of Bun is running?

1.0.3+8677ae9fb154dea49939dd396fdd1363959f96de

What platform is your computer?

Darwin 22.5.0 arm64 arm

What steps can reproduce the bug?

console.log("long/long".padEnd(15), new Date().toLocaleString("en-US", { dateStyle: "long", timeStyle: "long" }));
console.log("long/medium".padEnd(15), new Date().toLocaleString("en-US", { dateStyle: "long", timeStyle: "medium" }));
console.log("long/short".padEnd(15), new Date().toLocaleString("en-US", { dateStyle: "long", timeStyle: "short" }));
console.log("medium/long".padEnd(15), new Date().toLocaleString("en-US", { dateStyle: "medium", timeStyle: "long" }));
console.log("medium/medium".padEnd(15), new Date().toLocaleString("en-US", { dateStyle: "medium", timeStyle: "medium" }));
console.log("medium/short".padEnd(15), new Date().toLocaleString("en-US", { dateStyle: "medium", timeStyle: "short" }));
console.log("short/long".padEnd(15), new Date().toLocaleString("en-US", { dateStyle: "short", timeStyle: "long" }));
console.log("short/medium".padEnd(15), new Date().toLocaleString("en-US", { dateStyle: "short", timeStyle: "medium" }));
console.log("short/short".padEnd(15), new Date().toLocaleString("en-US", { dateStyle: "short", timeStyle: "short" }));

What is the expected behavior?

Node:

long/long       September 25, 2023 at 6:04:20 PM CDT
long/medium     September 25, 2023 at 6:04:20 PM
long/short      September 25, 2023 at 6:04 PM
medium/long     Sep 25, 2023, 6:04:20 PM CDT
medium/medium   Sep 25, 2023, 6:04:20 PM
medium/short    Sep 25, 2023, 6:04 PM
short/long      9/25/23, 6:04:20 PM CDT
short/medium    9/25/23, 6:04:20 PM
short/short     9/25/23, 6:04 PM

What do you see instead?

Bun:

long/long       September 25, 2023 at 6:04:32 PM CDT
long/medium     September 25, 2023 at 6:04:32 PM
long/short      September 25, 2023 at 6:04 PM
medium/long     Sep 25, 2023 at 6:04:32 PM CDT
medium/medium   Sep 25, 2023 at 6:04:33 PM
medium/short    Sep 25, 2023 at 6:04 PM
short/long      9/25/23, 6:04:33 PM CDT
short/medium    9/25/23, 6:04:33 PM
short/short     9/25/23, 6:04 PM

Additional information

In Date.toLocaleString with dateStyle set to "medium", bun uses "at" to separate the date and time, while Node/Chromium use ",".

[Electroid]

Would you mind checking this in Chrome vs Safari?

[bconnorwhite]

Interesting, Chrome matches Node but Safari matches Bun, so I assume this is V8 vs. JSC?

[Electroid]

@bconnorwhite Yep, looks like either V8 or WebKit is wrong here. Would have to take a look at the spec to see.

[cyfung1031]

You might ask in ECMAScript Internationalization API Specification as WebKit shall follow ECMA402 since 2016 (https://webkit.org/blog/6978/javascript-internationalization-api/)

However, the WebKit blog links to the spec published in June 2015, and there are still discussions on the displayStyle in 2016.
tc39/ecma402#108
There might be changes after WebKit adopted the Spec 2.0

You might also check the latest spec https://tc39.es/ecma402/2022/