Right now Tromsø loses 10 minutes of daylight a day. Ushuaia gains 4.

How long is daylight on 21 December?

Slide the lit part of the 24 hour day until it feels right for the city, then lock it in. Five cities, scored in minutes.

Every latitude, every day

Each pixel is the hours of daylight at one latitude on one day of 2026, from the sunrise equation. Dark purple is short, orange is about 12 hours, pale yellow is long. Tap or drag the dot, or use the sliders.

Play the year

Model, constants, sources

These are computed values, not station measurements. Nothing is fetched at runtime.

• Sunrise equation: cos H = (sin h0 - sin φ sin δ) / (cos φ cos δ), daylight = 2H / 15° per hour, with h0 = -0.833° for refraction and the solar disc, and polar night or midnight sun when the right side leaves the range -1 to 1. Wikipedia, Sunrise equation (secondary, cites Meeus, Astronomical Algorithms). NOAA also assumes 0.833°: NOAA GML, Solar Calculation Details.
• Solar declination: δ = -arcsin[0.39779 cos(0.98565° (N + 10) + 1.914° sin(0.98565° (N - 2)))], N counted from 0 on 1 January. Wikipedia, Position of the Sun (secondary).
• City coordinates: the coordinates in each city's English Wikipedia article (secondary), rounded to 0.01°.
• Times are local solar time, so clock time and daylight saving are left out. Mountains, clouds and the exact refraction at the horizon move real sunrises by minutes, more so near the poles.

Check against another source: monthly mean daylight hours in the climate boxes of four city articles (Helsinki, Tromsø, Anchorage, Quito, all secondary) against this model averaged per month.

The Anchorage source rounds to whole hours, so its gap is partly rounding.