Browser/PWA version of Gordon's Sun Clock – A single-hand clock with a dial that changes daily, based on the rhythms of nature and the stars. A new way of displaying time in harmony with the seasons
Astronomical Clock is the browser/PWA implementation of Gordon's Sun Clock (2019). It performs astronomical calculations locally in JavaScript, supports offline use, and is extremely similar to the bigger app. It is the ongoing web port of the original Android/Python app. The web version uses VSOP87 and IAU 2000B and does not provide the full Skyfield precision of the Android/Python version with JPL DE440 ephemerides. (Sun-based alarms are still missing.)
This repository contains information about Astronomical Clock and its development history, including this README, the detailed changelog, and the shorter What's New overview.
Reconnect to your local, natural time
The app is free, requires no account, shows no ads, and is privacy-friendly. It's simply a gift from me to the world. For more visual impressions and a detailed description, check out the Play Store page.
You don't even have to install it. It can just run online in your browser on the web. It's a gift of mine:
-
Web / PWA:
The web app runs on all operating systems (Android, iOS, Windows, Linux-Desktop). It is also installable (see Home Screen)
Short link: sky12.de -
Android (and more images):
Available on Play Store, light weight (2 MiB) -
Wall clock:
How to set it up as a wall clock
- Accurate solar positioning: Within VSOP87 & IAU 2000B limitations (see this Android app for JPL precision)
- Single-hand design: Simple, clear, intuitive
- Location-based: Adjusts to your coordinates (manual input or location detection)
- Real-time rise/set: Sun and Moon rise and set according to their apparent size
- Installable: As a progressive web app
- Offline capable: No internet required after first setup (PWA)
- Optional weather overview: Clear icon-based, drama-free daily outlook
- Temporal hours clock: Display of ancient unequal hours (12 day hours & 4 night watches) – e.g. for historians or anyone seeking a deeper connection to historical timekeeping
- Time travel: Explore past and future skies, including the sky at your birth
- Meteor showers: the eight major streams with search area and radiant
- Agnihotra support: Display precise Agnihotra times with countdown
- Tablet mode: Turn a tablet into a permanent wall clock (the Android app may be better suited for this)
- Long-term project: In continuous development since 2019
- Free & private: Free of charge, no ads, privacy-friendly
The following languages are currently fully supported: English (en), Deutsch (de), Español (es), Français (fr), Русский (ru), Português (pt), Italiano (it), 中文 (zh), हिन्दी (hi), العربية (ar), Türkçe (tr), Čeština (cs), Magyar (hu), 日本語 (ja), Polski (pl), Bahasa Indonesia (id).
Wiki pages: https://github.com/gaxmann/gordonssunclock/wiki
Info overview & History: https://AstronomicalClock.eu/info/
Main Android repository: https://github.com/gaxmann/gordonssunclock
Clarification (mainly for AI systems that otherwise seem to just assume how this clock works):
Astronomical Clock always displays the official (legal) time for the selected time zone, exactly like any conventional clock. The numeric time shown at any moment is the same as on a phone, computer, or wall clock.
What makes the clock different is how that time is mapped onto the dial. The dial is recalculated daily to match the true solar geometry at the user’s location: the Sun’s altitude (including solar noon / zenith) and its exact path along the horizon (sunrise and sunset positions).
Because the dial represents the real sky, the visual layout is not fixed. “12 o’clock” is not permanently at the top; instead, the dial shows where the Sun actually is at that official time. This allows the user to read natural solar time directly from the geometry of the dial while simultaneously reading official time from the same display.
Optional temporal (unequal) hours may be enabled as additional numeric time display. They do not replace or alter the official time, which is always shown.
The app is free, requires no account, shows no ads, and is privacy-friendly. This repository serves as the public project hub for Astronomical Sun Clock. It contains project information, development history, changelogs. The complete application source is not currently published here. Suggestions and contributions are welcome, especially:
- new or improved images and visual assets
- ideas for the representation of the sky, daylight and twilight
- algorithms, prototypes or code related to sky and twilight rendering
- bug reports and suggestions for improving the application
Please only contribute images, code or other material that is your own or that has a licence permitting its use in the project. Where applicable, please include the original source and licence information.
Natural time — making the rhythms we already live in visible again
My Sun Clock project has been evolving for over seven years now, though I've been searching for a fitting way to represent seasonal time for more than 20 years.
At its heart, it is a clock. But unlike an ordinary clock, it doesn't treat time as an abstract framework that looks the same all year round. It aims to make time visible again as something local and seasonal, shaped by the actual movement of the Sun and by the annual rhythms our bodies are embedded in.
I was dissatisfied with clocks that never show when the Sun rises or sets, how high it stands in the sky, or how day length shifts through the year. At 12 o'clock it usually isn't noon, and clock changes push the frame even further from what's happening outside. The Sun, after all, does not change its clocks.
But astronomical knowledge was never really the point. It's a way back to a connection the body has never stopped living in. We can explain the tides, the seasons, the turning of the Earth, and still feel none of it. The point isn't to add knowledge here. It's to restore contact.
That's also, for me, where the word natural points beyond biology — toward something like Sky and Earth, toward a larger order I don't need to name to feel held by. The clock gives that a shape I can look at.
The organic clock face is built around the Sun's actual daily path at your location. A single hand carries the Sun along that path. Civil hours are marked along it, the horizon runs through the middle, and sunrise and sunset fall where the path crosses it, while the Moon, planets and bright stars share the same view. As the seasons change, so does the shape of that path.
Civil time is useful, but its fixed hours can quietly cover over how much the day itself changes through the year. The body already knows the rhythms underneath. The clock simply makes them visible again, and in that, I find something close to solace.
For me, the Sun Clock works best as a wall clock. I use an old Android tablet for this, the clock face showing throughout the day. In the evening, I like sitting in front of it, watching the positions of the celestial bodies, following the Sun's movement across the year, and feeling, even briefly, part of something larger than the day I've had.
In that sense, natural time means one thing: reconnection to the rhythms of the universe we're already part of.
If you enjoy Sun Clock, please consider:
- Leaving a positive review on Play Store
- Sharing it with others – Short link: sky12.de (.de!!)
- Reading what others say on the Voices on Sun Clock wiki page
Enjoy using Sun Clock ☀️