Jason Williams @jason-williams.co.uk · 14/08/2026Agree, the govt need a “warning” level that just sends a normal text 020
Jason Williams @jason-williams.co.uk · 01/05/2026Excited about this, we've been working on the upcoming Container Timing API. Want to learn more? Take a read of the blog post below, put together with @tunetheweb.com and @jdapena.bsky.social. Feedback is very welcome. Try it out and help us shape this API! [This feature is Mozilla Approved] 0142
Reposted by Jason WilliamsHenri Helvetica 🧑🏾🚀🇭🇹 @henrihelvetica.bsky.social · 15/04/2026Had a delightful session today. A great conversation was had w/ @jdapena.bsky.social of @igalia.com about the work being done w/ container timing in Chrome. Both @jason-williams.co.uk + @andydavies.me got mentions. 🙃 This should be published soon. Thx to all who joined in! 072
Jason Williams @jason-williams.co.uk · 30/03/2026I will be speaking at #JSNation about Boa: A JavaScript engine in Rust. The Journey, what it taught me and how it works. Check out my #JSNation badge: gitnation.com/badges/jsnat.... Register via the badge and watch the stream for FREE! See you on June 11 & 15.gitnation.comCheck out my badge & claim your free JSNation 2026 remote ticket!Join 10k engineers worldwide at JSNation 2026 and meet 50 top speakers at June 11 - 15, 2026 0141
Reposted by Jason WilliamsRob Palmer @robpalmer.bsky.social · 26/03/2026Container Timing is a new web performance metric to measure when an area of the screen gets painted ⏲️ @jdapena.bsky.social and @jason-williams.co.uk have been working on it for the last couple of years. It's in Chromium, behind a flag. Hopefully coming to an origin-trial near you soon! 0246
Jason Williams @jason-williams.co.uk · 18/03/2026Thanks all for watching both in person and on the @londonwebstandards.org site! It was a pleasure to present at State Of The Browser 2026 (despite going over time!), hope to be back again next year #sotb 0144
Reposted by Jason WilliamsLondon Web Standards @londonwebstandards.org · 18/03/2026The recording of @jason-williams.co.uk talk ‘Temporal: It’s about time!’ is now available to watch online! 2026.stateofthebrowser.com/speaker/jaso... And Temporal has reached Stage 4: www.igalia.com/2026/03/13/T... 11412
Reposted by Jason WilliamsStuart Langridge @sil.kryogenix.org · 18/03/2026good talk from @jason-williams.co.uk at #SotB26 2026.stateofthebrowser.com/speaker/jaso... about Temporal, the thing that will sweep Date.parse() out of our horrified memories and into the dustbin of history (finally, hooray)2026.stateofthebrowser.comJason Williams | State of the BrowserJason Williams is a senior software engineer on Bloomberg’s performance team and the creator of the Boa JavaScript engine, an experimental Rust-based engine for the web. With two decades of experience... 181
Jason Williams @jason-williams.co.uk · 11/03/2026Temporal is now Stage 4 at TC39 🎂🎂🎂 Thanks to all the other champions of JavaScript's new date-time API. It has been a wild ride over many years! I wrote a blog post explaining how we got here 📜 bloomberg.github.io/js-blog/post... 2034782
Jason Williams @jason-williams.co.uk · 01/03/2026Wow, was not expecting the mention from my talk to have that much of an effect, sorry @samwho.dev 😂, yes this was from #SotB26, it’s a good resource! 1282
Reposted by Jason WilliamsOliver Turner @oliverturner.cloud · 28/02/2026@jason-williams.co.uk LOVED the talk, congrats on absolutely smashing it despite the residue of illness 🙌 Hadn’t realised that the Promise method you were referring to was allSettled… thanks so much for delivering my favourite addition 🫶 0121
Reposted by Jason WilliamsRob Palmer @robpalmer.bsky.social · 25/02/2026Container Timing - a new W3C performance metric - has migrated from Bloomberg to the WICG Github org 🎉 @jason-williams.co.uk made the Bloomberg Terminal use this web metric to measure human-perceived time to start apps. We've found it more useful than existing metrics. github.com/WICG/contain...github.comGitHub - WICG/container-timing: Container TimingContainer Timing. Contribute to WICG/container-timing development by creating an account on GitHub. 2376
Jason Williams @jason-williams.co.uk · 23/01/2026I’ve asked this for ages now, it would be good to see dependents ordered by most downloaded. That way, when a breach happens you can quickly see where the next biggest attack surface is. 170
Reposted by Jason WilliamsRob Palmer @robpalmer.bsky.social · 13/01/2026By many metrics the new Temporal date-time API is the single biggest change to JS ever 🔥 Like Kiesel, V8 chose to reuse Boa's open source Rust-based temporal_rs by @jason-williams.co.uk from TechAtBloomberg, Kevin Ness & Manish 👍 boajs.dev/blog/2025/09...boajs.devTemporal_rs is here! The datetime library powering Temporal in Boa, Kiesel, and V8 | Boa JSTemporal_rs is here! The datetime library powering Temporal in Boa, Kiesel, and V8 1204
Jason Williams @jason-williams.co.uk · 12/01/2026Great post Phil > Temporal has still not made it to many JavaScript engines. At the time of writing, it is available in Firefox and nowhere else It is some JS engines! It has been in Chrome Canary and is rolling out to stable (v144) now, powered by github.com/boa-dev/temp...github.comGitHub - boa-dev/temporal: A Rust implementation of ECMAScript's Temporal APIA Rust implementation of ECMAScript's Temporal API - boa-dev/temporal 170
Reposted by Jason WilliamsRob Palmer @robpalmer.bsky.social · 09/01/2026State of the Browser 2026 🎉 28th Feb in London 🇬🇧 @jason-williams.co.uk will present "It's about time" discussing the new JavaScript Temporal API ⌚ 1153
Reposted by Jason WilliamsDave Letorey @letorey.co.uk · 07/01/2026I built a countdown to State of the Browser using #TemporalAPI codepen.io/CodeRedDigit... Come see @jason-williams.co.uk talk about itcodepen.ioTime until State of the Browser 2026... 022
Jason Williams @jason-williams.co.uk · 19/12/2025Woo! Cannot wait to speak at State Of The Browser 2026. Looking forward to meeting other people in this space too, see you next year! 0306
Reposted by Jason WilliamsMary Branscombe @marypcbuk.bsky.social · 12/12/2025I've been writing about Temporal (what @b.trl.sn calls 'the fix for our broken date object' which is so bad @samwho.dev made a quiz) for a long time and this time, maybe this time, it's really time for temporal @jason-williams.co.uk tells me, which will make @bkardell.com and many developers happythenewstack.ioES2026 Solves JavaScript Headaches With Dates, Math and ModulesWith ECMAScript 2026, JavaScript will get more precise about sums, errors, international dates and times — and it may finally be time for Temporal. 282
Reposted by Jason WilliamsRob Palmer @robpalmer.bsky.social · 09/12/2025ECMAScript excitement 😉 A highly comprehensive article on what will (and might!) land in ES2026 by @marypcbuk.bsky.social 🎉 Includes coverage on Temporal by Boa creator @jason-williams.co.uk who leads the Rust-based temporal_rs library, as used by Google's V8 engine, amongst others. 0317
Jason Williams @jason-williams.co.uk · 15/11/2025Fancy seeing @boajs.dev trending on hacker news! news.ycombinator.com/item?id=4583...news.ycombinator.comBoa: A standard-conforming embeddable JavaScript engine written in Rust | Hacker News 050
Reposted by Jason WilliamsRob Palmer @robpalmer.bsky.social · 04/11/2025ECMAScript excitement 😉 Congrats to @manishearth.bsky.social on unflagging TC39 Stage 3 Temporal in V8 today. Heading for Chrome 144 🎉 By many metrics this new date-time API is the single biggest change to JS ever 🔥 V8 uses Boa's temporal_rs by @jason-williams.co.uk Kevin Ness & Manish 👍 516130
Jason Williams @jason-williams.co.uk · 31/10/2025Thanks @mmocny.com for the container timing shoutout and stealing my low effort diagram 😂 Great talk @ #perfnow 1184
Reposted by Jason WilliamsBoa @boajs.dev · 23/10/2025Boa v0.21 has been released! Plenty of new features, builtins and performance improvements. Blog post with details boajs.dev/blog/2025/10... Discussions: Lobste.rs: lobste.rs/s/upi3xa/boa... news.ycombinator.com/item?id=4567... www.reddit.com/r/rust/comme...boajs.devBoa release v0.21 | Boa JSBoa release v0.21 021
Jason Williams @jason-williams.co.uk · 24/09/2025Some other discussion links news.ycombinator.com/item?id=4536... www.reddit.com/r/rust/s/J4C...news.ycombinator.comTemporal_rs is here! The datetime library powering Temporal in Boa and V8 | Hacker News 040
Jason Williams @jason-williams.co.uk · 24/09/2025This is huge, Temporal is on its way, its been a long effort and great to see collaboration on a centralized Rust library including V8 who have never integrated Rust before now! Shout out to everyone who has been involved. Much more info in the blog post! 0336
Reposted by Jason WilliamsNicholas Nethercote @nnethercote.bsky.social · 18/07/2025New blog post: I am a Rust compiler engineer looking for a new job nnethercote.github.io/2025/07/18/l...nnethercote.github.ioI am a Rust compiler engineer looking for a new jobFor the past 3.75 years I have been fortunate to work on Futurewei’s Rust team, where I had enormous freedom to “make Rust better” however I see fit. It has been the highlight of my career and I am gr... 58543
Jason Williams @jason-williams.co.uk · 17/07/2025Hey thanks for the inclusion @infrequently.org, I feel honoured! 010
Jason Williams @jason-williams.co.uk · 16/07/2025I’ve added support for the DAP “startDebugging” request in the Helix Editor. This means you can now debug JavaScript/TypeScript! It has been released in v25.07 helix-editor.com/news/release... PR: github.com/helix-editor...helix-editor.com Release 25.07 Highlights | Helix A post-modern modal text editor. 010
Reposted by Jason WilliamsRob Palmer @robpalmer.bsky.social · 22/06/2025Boa's temporal_js may turn out to be one of the most widely used implementations of the TC39 Stage 3 Temporal API 👍 An independent open source project having impact on the whole JS ecosystem. The Boa community has come along way since it was started by @jason-williams.co.uk seven years ago. 1468
Jason Williams @jason-williams.co.uk · 26/02/2025Looking forward! You may also be interested in the Web Preferences API proposal which allows sites to set the override the color scheme and have the browser remember it. github.com/WICG/web-pre... this is now part of media-queries-5.github.comGitHub - WICG/web-preferences-api: The Web Preference API aims to provide a way for sites to override the value for a given user preference (e.g. color-scheme preference) in a way that fully integrate...The Web Preference API aims to provide a way for sites to override the value for a given user preference (e.g. color-scheme preference) in a way that fully integrates with existing Web APIs. - WICG... 020
Reposted by Jason WilliamsRachel Andrew @rachelandrew.co.uk · 13/02/2025Interop 2025 launched today! Some really exciting features set to become part of Baseline this year.web.devInterop 2025: another year of web platform improvements | Blog | web.devDiscover the features included in Interop 2025. 04018
Jason Williams @jason-williams.co.uk · 30/01/2025I’ve been helping (alongside others) to Champion Temporal for around 6 years now, it’s great to see it approaching the finish line. The responses have been positive. Great work @joshcena.com and @meyerweb.com on the MDN documentation, momentous effort. Also props to the main man @ptomato.name 1428
Jason Williams @jason-williams.co.uk · 24/01/2025Myself and @pcwilliams.net continue to be humbled by the response we had at @perfnow.bsky.social. Our talk “Bloomberg Becomes Browser” has been published! You can watch it here: youtu.be/y1MCLZm8yAY?...youtu.beBloomberg Becomes Browser | Jason Williams & Paul Williams | performance.now() 2024YouTube video by Web Conferences Amsterdam 2187
Jason Williams @jason-williams.co.uk · 14/12/2024Fantastic to see @boajs.dev at the top of JS Weekly! Nice snake illustration too. There’s some good changes in this release and more coming up for 2025. “This is no toy engine” - javascriptweekly.com/issues/716 CC @cooperx86.bsky.social 1123
Reposted by Jason WilliamsBoa @boajs.dev · 05/12/2024We have released v0.20! This release includes more features, runtime additions, performance optimizations and more. boajs.dev/blog/2024/12... CC @thisweekinrust.bsky.socialboajs.devBoa release v0.20 | Boa JSBoa release v0.20 031
Jason Williams @jason-williams.co.uk · 04/12/2024I have used DCL a couple of times but I’ve never used L or FP 010
Reposted by Jason WilliamsWebPerfWG @webperfwg.org · 22/11/2024In our meeting yesterday, we decided to adopt Element Timing (and the followup Container Timing work) into the working group. CfC coming up!! We also discussed some upcoming improvements to the crash reporting API (still in incubation). Minutes: w3c.github.io/web-performa...w3c.github.io 03116
Jason Williams @jason-williams.co.uk · 22/11/2024Well that's made my day, jQuery was one of the first open source projects I ever contributed to (~2010!) 👋 @johnresig.com 1141
Jason Williams @jason-williams.co.uk · 16/11/2024Thanks to everyone at @perfnow.bsky.social for making us feel welcome and putting on a good conference. Really enjoyed meeting you all! 091
Reposted by Jason WilliamsBjörn Peter @spielzeugpferd.bsky.social · 15/11/2024Crazy refreshing and insightful talk by @jasew.bsky.social & @pcwilliams.bsky.social at #perfNow! This could have continued for another hour only talking about the Container Timing API alone for my taste. Brilliant! 162
Reposted by Jason WilliamsPaul Williams @pcwilliams.net · 15/11/2024Today @jasew.bsky.social and I tell the story of how our team embedded web technology to give us the best combination of real-time data and rich UI for the #BloombergTerminal. It is an honour to speak at @perfnow.bsky.social. The #PerfNow team have been so welcoming. perfnow.nl/speakers#paulw 5205
Reposted by Jason WilliamsRob Palmer @robpalmer.bsky.social · 13/11/2024The @perfnow.bsky.social conference begins tomorrow in Amsterdam. It is going to be great 👍 For the first time @pcwilliams.bsky.social & @jasew.bsky.social will share the story of how the Bloomberg Terminal uses web tech & what this means for the wider web ecosystem 🎉 If you see us, come say hi 👋 2173
![Code example showing the usage of Temporal.ZoneddateTime
```js
// London DST starts: 2026-03-29 01:00 -> 02:00
const zdt = Temporal.ZonedDateTime.from(
"2026-03-29T00:30:00+00:00[Europe/London]",
);
console.log(zdt.toString());
// → "2026-03-29T00:30:00+00:00[Europe/London]"
const plus1h = zdt.add({ hours: 1 });
console.log(plus1h.toString());
// "2026-03-29T02:30:00+01:00[Europe/London]" (01:30 doesn't exist)
```](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:r5emt2gkdrkb2yc6y7xndxpe/bafkreicgonzisednk3qegophndqf6fnslwtvbd7gshsgtv6fpi3arh2dsi)
