I
Day
When the sun rises and sets, how high it stands at noon, how long the day is. Beside it a 24-hour dial, midnight at the top: the arcs are the daylight.
Example · Berlin & Cape Town
The day, counted twice.
Sun position, twilight phases and day length for two places on Earth — side by side, for any date, worked out live in your browser.
- Day length Berlin
- 11:36:27
- Day length Cape Town
- 12:25:32
- Difference
- +0:49:05
A clock time doesn't tell you how light it is.
If you talk to people in other time zones, you convert constantly — and still get it wrong. Seven hours' difference doesn't mean it gets light seven hours later there.
So Solaris Dual doesn't answer “what time is it there”. It answers “how far along is the day there”. Sunrise and sunset, twilight, day length — for both places, side by side.
And it follows one rule throughout: place A is the baseline, every difference applies to place B. All times are local; the time-zone offset is not folded into the differences.
Four views of the same day
II
Twilight
Every phase from astronomical twilight to the golden hour, morning and evening, for both places. The phase dial shows one place on the outside, the other on the inside.
III
Year
How day length shifts across the year, with equinoxes and solstices. Where the two rings of the year dial cross, both places get the same amount of light.
IV
Places
Search anywhere via OpenStreetMap, reference places from Tromsø to Quito, ready-made extreme pairs. The earth section shows the day and night side on the chosen date.
Two places in one picture.
Four drawings, one idea: the two places don't sit side by side in two charts, they sit together in one. The distance between them is the point.
Everything in it
Sun position
- Sunrise and sunset to the second
- Solar noon
- Altitude at noon
- Sun altitude now
- Azimuth at rise and set
- Change from previous day
Twilight
- Astronomical, nautical, civil
- Blue hour
- Golden hour
- Length of twilight
- Astronomical night
- Best light today
Year
- Day length for every day
- Equinoxes and solstices
- Light in the year
- Amplitude
- Longest day
- Budget so far
Places
- Search worldwide via OpenStreetMap
- Reference places
- Solar extreme pairs
- Latitude delta
- Antipodal offset
Comparison
- Every figure for both places
- Differences with a sign
- Local time, not converted
- A note when the time zones differ
- Place colours throughout
Controls
- Any date
- Your system's date picker
- Swap places
- Time-of-day slider
- Copy as text
- Phone and desktop
Your browser does the calculating.
- No sign-up, no account. There is nothing for you to create.
- The calculating stays here. Sun position, twilight and the yearly curve are worked out by your browser. Nothing goes out for that.
- Place search asks Photon (Komoot, using OpenStreetMap data) — only when you search, and only with what you type.
- No cookies. Visits are counted without cookies, on Boris's own server.
- The fonts are here. Nothing is loaded from Google.