Explore day length city by city on an interactive map. Pick a country and date, and see how the day grows longer toward the south and shorter toward the north.
Shorter day ← → longer day. Tap a city for details.
City data: GeoNames (CC BY 4.0)
The map shows day length city by city for a chosen date. Pick a country, move the date, and the pattern emerges: day length settles into horizontal bands, where cities on the same latitude get practically the same number of daylight hours no matter how far apart they are east to west.
In summer the bands brighten towards the north, in winter towards the south. This is not a quirk of the particular cities on the map — it follows directly from the fact that the Sun's height above the horizon depends only on latitude and the date. Longitude shifts the clock times of sunrise and sunset, but not the number of hours between them.
Even across a single country the difference is measurable. On 21 June London gets about 16 hours 38 minutes of daylight while Edinburgh, 530 km north, gets about 17 hours 37 minutes. Carry on north to Arctic Norway and sunset disappears entirely for weeks at a time.
A map of day length says nothing about how light it actually feels. Two cities with the same number of daylight hours can experience the day very differently, because the sun's elevation differs: the further north, the lower the sun sits at midday, and the longer and softer the twilight. In London it takes about 48 minutes from sunset until it gets properly dark in June, while in Singapore it takes barely more than 20.
That is also why northern summer evenings feel longer than the numbers suggest. The sun travels down towards the horizon at a shallow angle and lingers just below it, so the evening light drags on well after sunset has passed.
The boundary between the lit and unlit halves of the Earth is called the terminator, and watching how it moves across the map through the year is the quickest way to understand why seasons work the way they do.
It is never a straight line down the map, except on two days a year. Because the Earth's axis is tilted about 23.4° from vertical, the circle of illumination is tilted with respect to the poles — so the terminator cuts across the latitudes at an angle, and it is the size of that angle that decides how unequal day and night are.
At the equinoxes in March and September, the tilt is side-on to the sun and the terminator passes exactly through both poles. Every point on Earth spends the same time on each side of it, which is the geometric meaning of "equal night". At the solstices the tilt is at its most pronounced: the terminator swings so far off the poles that an entire cap at one end of the planet sits permanently in light and the other permanently in shadow. That is the midnight sun and the polar night, and on the map you can watch the caps grow and shrink as you move the date.
This is the distinction the map makes obvious, and it is worth stating separately because it is so often conflated. Two cities at the same latitude but different longitudes get the same amount of daylight on any given date, but at different clock times. Two cities at the same longitude but different latitudes get daylight at broadly similar clock times, but in very different quantities.
What complicates the picture on the ground is that clock time is political, not astronomical. Timezones are drawn as wide blocks, and a place at the western edge of a zone experiences solar noon much later on the clock than a place at the eastern edge. Spain is the standard example: geographically it sits under the same meridian as Britain, but it keeps central European time, so the sun sets there strikingly late in the evening by the clock — with no extra daylight involved at all. China running a single timezone across a span that ought to be five is the same effect, taken to an extreme.
The same logic explains what daylight saving time does and does not do. It moves the clock, not the sun.
Beyond the twilight point above, there is a second thing hours of daylight cannot capture: how high the sun gets. Sun elevation at noon depends on latitude and date, and it drives nearly everything about the character of the light — how strong the UV is, how warm the ground gets, how long the shadows are.
The maximum midday altitude at a given place is roughly 90° minus your latitude, plus or minus the 23.4° tilt depending on the season. In London that means a sun about 62° up at midsummer noon but barely 15° at midwinter — low enough that it never really warms anything, and low enough that the UV index stays near zero for months. In Singapore it passes almost directly overhead twice a year. Two places can share a day length and have almost nothing else in common.
To go further: compare specific cities on the comparison page, see the whole annual curve for one place on the year chart, or spin the 3D globe to see the terminator on a sphere rather than flattened onto a projection.
Because the Sun's height above the horizon depends only on latitude and the date. Longitude shifts the clock times of sunrise and sunset, but not the number of hours between them.
On 21 June London gets about 16 hours 38 minutes of daylight while Edinburgh, 530 km north, gets about 17 hours 37 minutes. In winter the picture reverses.
Because the sun travels down towards the horizon at a shallow angle and lingers just below it. In London it takes about 48 minutes from sunset until it gets properly dark in June, while in Singapore it takes barely more than 20.