What this tool is, and who it is for
High-latitude trips fail in the dark more often than they fail in the storm. This calculator solves that problem with the standard NOAA solar algorithm: it accepts any latitude, longitude and date, and returns sunrise, sunset, civil and nautical twilight, solar noon, day length and the golden hour window. The output is plain local clock time, suitable for printing and taking on the trip. The honest-limits panel flags where the math degrades — within 100 km of the poles, and around polar day and night — and where terrain in the picture can change the answer materially.
Local solar time is reported, so figure in time zone and daylight saving yourself.
Positive north, negative south.
Positive east, negative west.
Sunrise 05:35 · sunset 18:13 local solar time.
Artificial light needed below this.
Morning: 05:09–06:33
Evening: 17:15–18:39
Step-by-step user guide
How to operate the calculator in your browser, what to enter, and what to do with the result.
- 01
Enter the latitude and longitude of the start point of the day. Use degrees with decimals; the tool accepts both positive and negative values.
- 02
Set the date for which you want daylight figures.
- 03
Choose the time zone offset in hours from UTC. The output is in local clock time at that offset, without daylight saving shifts.
- 04
Read sunrise, sunset, twilight windows and golden hour. The day-length line tells you the total usable light.
- 05
Compare the result against your planned walking day. If the planned duration exceeds usable daylight, the verdict field will flag it.
What the calculator actually does with the numbers you enter
- 01
Solar position is computed with the standard approximation of the NOAA solar calculation algorithm, which is accurate to roughly one minute for civil latitudes.
- 02
Sunrise and sunset use a zenith angle of 90.833 degrees, accounting for atmospheric refraction and the solar disc radius — the standard definition.
- 03
Civil twilight uses a zenith angle of 96 degrees, the point at which artificial light becomes necessary for most activities.
- 04
Golden hour is defined as the period when the sun sits between the horizon and 6 degrees of elevation, following common photographic convention.
Published sources behind the formulas
- [1]Solar calculation algorithms and documentationNOAA Global Monitoring Laboratory · 2025
- [2]Astronomical definitions of twilightInternational Astronomical Union · 2024
- [3]Daylight and golden hour planning for photographyRoyal Photographic Society · 2024
Frequently asked questions
Short, sourced answers to the questions readers send us most often about this calculator.
How does terrain shadow change this?
Substantially. A north-facing valley can lose more than an hour of usable light compared with the open-sky calculation, and a steep ridge to the east can delay apparent sunrise by 30 minutes or more. The calculator models the open sky, not your horizon. Combine the result with a sketch of the local terrain before committing to an alpine start.
What does civil twilight actually mean?
Civil twilight is the period after sunset or before sunrise when the sun is between 0 and 6 degrees below the horizon. There is enough natural light for most purposes without artificial sources, but the landscape is in deep shadow. For most walking, you can plan until the end of civil twilight and treat the next hour as headlamp time.
Does it work at extreme latitudes?
Yes, with the caveat that the approximation degrades within roughly 100 km of the poles and around polar day and night. Above roughly 70 degrees latitude, day length becomes extremely sensitive to small changes in date, and a one-degree error in latitude can shift sunrise by several minutes. Use the result as a starting point and verify against an almanac for serious polar planning.
How does cloud cover change it?
It doesn't, in this calculator. Cloud cover reduces light well before sunset but does not change the geometric sunrise or sunset. Treat the result as the open-sky best case; budget additional margin in marginal conditions.