Day Length Changes

Daylight length shifts with the seasons — fastest around the equinoxes and flattest near the solstices. Pick a city to see today’s daylight and the change through the year.

How to read day-length changes

Compare daylight length and its daily change to see whether days are growing longer, shorter, or nearing a seasonal turning point.

Fastest around the equinoxes — Near the spring and autumn equinoxes the daily change is largest — at mid latitudes a day can differ by two or three minutes from the last.
Flattest near the solstices — Near the summer (longest) and winter (shortest) solstices the change approaches zero, and consecutive days are almost the same length.
Bigger swings at higher latitudes — Closer to the poles the seasonal range is larger; near the equator daylight stays close to 12 hours all year with little change.

FAQ

How is daylight length calculated?

It is sunset minus sunrise, using the standard definition of the sun’s centre crossing -0.833° (including atmospheric refraction).

Why is the daily change not constant?

Daylight length follows a sine curve: the slope is steepest near the equinoxes (fastest change) and near zero around the solstices (almost no change).

Are the longest and shortest days always the solstices?

Roughly, yes — but the earliest sunrise and latest sunset don’t fall exactly on the solstice due to the equation of time. This tool scans the whole year for the actual longest and shortest daylight.

Shadow multiple = 1 ÷ tan(elevation) — At 45° the shadow equals the object’s height; the lower the sun, the longer the shadow; at solar noon the sun is highest and the shadow shortest.
Estimate an object’s height — Measure the shadow length and divide by the current shadow multiple to estimate the height of buildings, trees or flagpoles that are hard to measure directly.
Plan light direction and shading — Azimuth tells you the direction of the sun and shadow — useful for finding front- or back-light in photography, and for assessing shade and daylight in buildings.

Golden hour: roughly an hour after sunrise and before sunset — When the sun is near the horizon (about 0°–6°) the light is soft and warm with long shadows — great for landscapes, portraits and backlight.
Blue hour: before sunrise and after sunset — When the sun is below the horizon (about 0° to -6°) the sky turns a saturated deep blue — ideal for cityscapes and reflections.
Arrive 15 minutes early — Golden and blue hours change fast. Arrive early, set up the tripod and frame your shot so you can shoot continuously once the light arrives.

Place the camera position first — The city picker only gets you nearby. For real planning, click the map or drag the blue pin to where you will stand: a bridge, seawall, viewpoint, or street corner.
Then choose the shooting date — At the same location, sunrise and sunset bearings change a lot through the year. For sun-through-building or moon-over-ridge shots, the date is often more important than the minute.
Find the alignment time — Move the time slider and watch the right panel update azimuth and altitude for the sun, moon, and galactic core. When a line crosses your foreground direction, that time is worth scouting.