Have you spotted something wrong, got a suggestion, or just want to say hello? Send us a message using the form below and we'll get back to you. We read everything.
If you would rather write directly, the address is contact@daylighthours.app. The site is published by Henrik Lund Thomassen.
These are the messages we most want to receive, and the ones we act on fastest. To make a report useful, please include three things: the place (a city name is fine, coordinates are better), the date, and what you expected to see instead. A screenshot helps but is not necessary.
Before you write, it is worth checking the how we calculate the times page. A difference of a few minutes from what you observe is usually not a bug — our times assume a flat, unobstructed horizon at sea level, so hills, buildings and treelines will all take the sun earlier than we predict. Differences of more than about ten minutes, or anything near a timezone boundary or above the Arctic Circle, are worth telling us about.
We are a small project and cannot build everything, but we would rather hear an idea and decline it than never hear it. Requests that explain what you were trying to do are far more useful than requests that specify a solution — knowing the underlying need often leads somewhere better than the feature originally asked for.
The sun and moon figures are calculated with the open-source SunCalc library rather than licensed from a data provider, so there is nothing proprietary about the underlying astronomy. If you want to show live day-length data on your own site, the simplest route is our embeddable widget, which needs no account and no API key. For anything beyond that — bulk use, or an integration you would like us to know about — please get in touch and say what you have in mind. The terms of use set out the limits.
We are not a weather service and do not hold forecast, rainfall or temperature data. We also cannot advise on aviation, maritime, legal or religious observance timing — our times are calculated for general use and are not certified for any of those purposes. If your use is safety-critical, please use an official source for your jurisdiction.
This is a side project rather than a staffed support desk, so replies typically take a few days and occasionally longer during holidays. Bug reports and corrections are prioritised over everything else. We do not send marketing email, and we do not pass your address to anyone.