PromoClock.One question, answered the instant you open it — in your timezone, in your language.

Every developer using Claude knows the frustration. Anthropic announced a promotion that doubles usage limits during off-peak hours — but the peak window is defined in US Eastern Time: 8 AM to 2 PM ET on weekdays. For anyone outside the United States, the immediate question is always the same: “What time is that for me?”

Twitter was full of developers doing timezone calculations by hand — converting ET to GMT, JST, IST, BRT and every other timezone, then trying to remember which way the clocks had moved for daylight saving. It was a solvable problem, and nobody had built a proper solution for it.

We decided not to just use the promotion and move on. We wanted to solve the problem properly — and ship it fast enough that people could actually use it while the promotion was still running.

PromoClock is a single-page web application built around one job: the moment you open it, a clear green or red indicator shows whether 2X limits are active, with a live countdown to the next change and a visual timeline of peak and off-peak windows mapped to your local time.

It auto-detects your device timezone through the browser's Intl API — no manual selection, no IP geolocation, no permissions — and loads in one of 10 languages (English, Hindi, Japanese, French, Portuguese, Korean, Spanish, German, Chinese and Turkish) based on your browser preference.

Then we kept going, because developers don't just want a status page — they want tools they can wire into their workflow:

We made a deliberate architectural choice: the entire 2X-detection logic runs client-side. No backend server, no database, no authentication. The app is a static site on a CDN — so it scales to any number of concurrent users with zero infrastructure cost, and response time depends on the nearest edge node, not a server.

The stack: React 19 with the React Compiler for automatic memoisation, Vite 8 for the build, and TypeScript throughout. The codebase is compact enough that the whole app — all 10 translations included — ships in a single bundle that loads in under a second on any connection.

PromoClock launched the same day Anthropic's March 2026 promotion went live. Within its first week it reached developers in over 90 countries, was featured in a detailed technical write-up on DEV Community, and was shared across X, LinkedIn and developer forums — with developers wiring the API into their own terminals and automations.

It's the clearest way we know to show what we can build: do it in public, for a real audience, solving a real problem. PromoClock reached more people in a week than most agency portfolio pieces ever will.