Sundial Screensaver
The Sundial screensaver is a working sundial that casts the gnomon's shadow to the Sun's true position right now, marking solar time and the analemma, computed on your device from the date and time. It needs no feed, runs in your browser, and ESC exits.
How the Sundial screensaver works
The saver computes the Sun's current altitude and azimuth for your location with standard solar equations, on your device.
A gnomon casts its shadow in the opposite direction to the Sun, lengthening near sunrise and sunset just as a real dial's would.
Hour lines mark solar time, and the difference between sundial time and clock time — the equation of time — is shown.
When the Sun is below the horizon the dial dims to a night state, and the analemma figure-eight can be drawn across the face.
A worked example
Through the day the shadow swings around the dial and shortens toward noon, reading solar time that runs a few minutes off the clock. Switch on the analemma and the Sun's noon positions trace the famous figure-eight across the face.
Settings & tips
- Location sets where the Sun's position is computed for.
- Show analemma draws the Sun's figure-eight of noon positions.
- Dial color recolours the sundial.
Frequently asked questions
- Does it tell the real time?
- It tells real solar time — what a sundial reads — which differs from clock time by a few minutes (the equation of time), shown on the dial.
- Does it need a connection?
- No. The Sun's position is computed on your device, so the sundial runs fully offline.
- What is the analemma?
- It's the figure-eight the Sun traces if you mark its position at clock-noon through the year, caused by Earth's tilt and elliptical orbit.
- What happens at night?
- When the Sun is down the dial dims and shows a night state, since there's no shadow to cast.
- Is it free?
- Yes — free, no download, no key, in your browser.