World Clock is a small Windows desktop app that shows the current time, date, and weather for a list of places you choose, one card per place. It’s free, open source (MIT), and has no backend.
Source code and docs: github.com/stewartisland/world-clock
Why I built it
I work with people in New Zealand, Croatia, the UK and the US in ET, CT and PT. Before I message or call anyone, I want to know what time it is there, and more importantly, what day it is.
None of the existing options quite fit:
- Windows’ built-in extra clocks only allow two additional time zones, and they’re buried in the taskbar flyout.
- Websites and phone apps work, but you can’t park them on a second monitor or keep them above your other windows.
- Most time zone tools don’t show the date, which is exactly what trips you up when one place is already into tomorrow.
So I wanted a lightweight native window that shows every place at once, with the day, the offset from me, and the weather, that I can reorder and keep on top.
What it does
Each card shows:
| Part | Example |
|---|---|
| Label | New York |
| Local time | 11:55 PM |
| Date | Monday, Sep 21 |
| Offset | UTC-4 · -16h from you |
| Weather | ☀️ 66° |
| Place the weather is for | New York, United States |
On top of that:
- Add a clock by searching for a city. Type “Dallas,” pick “Dallas, Texas, United States,” and the time zone and weather location are set for you. You can relabel it to anything (“Mum,” “Sydney office”).
- Drag to reorder, or right-click to move, rename, set location, or remove.
- Always on top, so it works as a small floating clock.
- Celsius or Fahrenheit, defaulting to your Windows region.
- Light, dark, or follow Windows, switching instantly.
- Sync across PCs with a personal Microsoft account. Your settings are stored in an app-only folder in your own OneDrive. The app can’t see any of your other files, and I never hold your data.
- Works offline. The clocks keep running. Weather greys out after 20 minutes without a connection and disappears after 2 hours, rather than showing a stale number as if it were current.
Daylight saving is handled by Windows itself, so time zone rule changes arrive through Windows Update with no app release needed.
How it was built
I built World Clock over two days, September 22 and 23, 2026, pair-programming with Claude Code, Anthropic’s AI coding agent.
The loop was simple: describe what I wanted in plain language, have Claude Code write and build the change, check it running, and adjust. Bigger features (weather, and sign-in with sync) got a written feature spec first, with the open questions put to me as explicit decisions before any code was written. The sync logic, the one place a bug could quietly lose someone’s data, has automated tests covering every first-sign-in and conflict path.
| Version | Date | What changed |
|---|---|---|
| 1.0 | Sep 22, 2026 | Six clocks, add/remove/reorder, always on top, settings saved locally |
| 1.1 | Sep 23, 2026 | Weather on each card, add a clock by city search, light and dark themes |
| 1.2 | Sep 23, 2026 | Simplified header, theme can follow Windows, versioning script |
The about page in the repo walks through the design decisions, including why it’s native WPF instead of Electron and why a wrong weather location must always be visible, never silent.
Requirements
- Windows, with the .NET 9 Desktop Runtime
- An internet connection for weather and city search (clocks work without one)
- A personal Microsoft account if you want sync (work and school accounts aren’t supported yet)
What’s next
Google account sync, more weather detail on hover, undo for removed clocks, color weather icons, and broader test coverage.
Credits
Weather and place data from Open-Meteo.com, licensed CC BY 4.0. Open-Meteo’s free tier is for non-commercial use, which is why World Clock is free with no ads.