Daylight Hours is a free web tool that shows you the sunrise time, sunset time and length of the day for any location on Earth — today, or on any date you choose. There is no sign-up, no paywall and no limit on how often you can use it.
The site is an independent project, driven by a simple fascination with how the rhythm of light changes through the year. It is published in two languages: English at daylighthours.app and Danish at dagenslaengde.dk. The two sites share the same engine and the same approach; they are not translations of each other, and each is written for its own readers.
The question that started it was an ordinary one: how much longer is the day than it was last week? It sounds trivial, and most sources answer it badly. They give you a sunrise time and leave you to do the arithmetic, or they bury the answer under a forecast you did not ask for. At high latitudes the answer is genuinely interesting — the day can grow by four minutes every twenty-four hours in March, which is a change you can feel — and it deserves to be shown properly rather than implied.
So the site leads with the answer. Day length first, in hours and minutes. Then how it has changed since yesterday, last week and last month. Then everything else.
Beyond the basic sunrise and sunset times, the site lets you explore the sun and moon in depth:
There are also reference articles on the things people actually search for — the longest and shortest days, the equinoxes, daylight saving time, and when it gets dark — written to be read rather than to be crawled.
All of the sun and moon figures on this site are computed astronomically using the well-established SunCalc library. We do not call an external weather or astronomy API for the sun data — the maths runs from your coordinates and the date you pick. This means the results can be computed for any coordinate on Earth without an outside lookup, and they keep working even on a slow connection. How close they sit to an independent ephemeris is measured on every build and published on the accuracy page — for most latitudes the difference is immaterial, but it grows towards the poles, where the sun meets the horizon so obliquely that small differences of model become minutes.
Because the calculation is purely geometric, the times we show are for a flat, unobstructed horizon. Your real-world sunrise or sunset can differ by several minutes if you are surrounded by mountains, tall buildings or hills. If you want the full picture — what counts as sunrise, how twilight is defined, what happens above the Arctic Circle, and where the UV numbers come from — we have written it all down on the how we calculate the times page.
We would rather be corrected than be wrong. If a figure looks off, particularly near a timezone boundary or at polar latitudes where the edge cases live, please tell us via the contact page — with the place, the date and what you expected. Reports like that have found real bugs before.
Daylight Hours is free to use and is funded by advertising. We keep the ads out of the way of the answer: never between you and the number you came for, and never on our legal or information pages. There is no tracking wall, no newsletter gate and no premium tier. You can create a free account if you want to save locations or receive notifications, but nothing on the site requires one. There is a newsletter about solstices, equinoxes and eclipses, but you switch it on yourself from your account page — it never stands between you and an answer.
We collect as little as we can. Your chosen location is stored in your own browser, not on our servers, unless you explicitly save it to an account. The details are in our privacy policy, and the conditions of use — including what the data may and may not be relied on for — are in our terms of use.
Daylight Hours and dagenslaengde.dk are published by Henrik Lund Thomassen. It is a private project with no company behind it and no editorial staff — worth knowing when you are deciding whether the figures are good enough for what you need them for. That is also why the checking is done by the build rather than by the author: every build recomputes the published figures against an independent ephemeris, and the result is on the accuracy page.
Spotted something wrong, or have an idea for the site? We would genuinely like to hear it — write to contact@daylighthours.app, or use the contact page. We read everything, even when we cannot act on it.