Polar Day / Night Checker
Explore how day length stretches toward 0 or 24 hours at high latitudes.
By Aryan Khan, Founder & Editor · Updated October 2026
For example, Tromsø, Norway (69.65°N) gets a geometric midnight-sun run from about May 23 to July 22 — and a matching polar-night stretch around the December solstice.
How to use Polar Day / Night Checker
Poleward of the circles, the daily rulebook breaks:
The Polar Day / Night Checker tells you whether the Sun rises at all — or sets at all — at a place on a date, from its latitude and the Sun's seasonal declination. Enter place and date and read the verdict: polar day, polar night, or an ordinary day.
- 1Set a high-latitude place and date.
- 2Read day length.
What people use Polar Day / Night Checker for
1. Arctic trip planning
Tromsø, Svalbard, northern Alaska: whether your July trip has a sunset (it may not) changes sleep, photos and sanity. The circles themselves are mapped on the Arctic Circle page.
2. Winter darkness checks
A December posting or expedition near the pole — how many weeks without sunrise is a logistics fact, not a vibe.
3. Teaching the seasons
The checker turns axial tilt into a yes/no answer students can test at any latitude — the Seasons by Latitude page explains the machinery.
4. Solar project screening
A site with a month of polar night has a solar problem no panel angle fixes; check before the feasibility study.
Worked examples
At 69.65°N the Sun stays up geometrically from about May 23 to July 22 (longer counting refraction and elevation), and stays down for a matching stretch centred on the December solstice.
Exactly on the Arctic Circle (66.56°N), the Sun just grazes: one day a year it never quite sets, one day it never quite rises — the line is drawn where the grazing happens.
How the windows grow with latitude
Approximate polar-day length at the summer solstice season, geometric.
| Latitude | Midnight-sun run |
|---|---|
| 66.56° (the circle) | ~1 day |
| 70° | ~two months |
| 75° | ~three and a half months |
| 80° | ~four and a half months |
| 90° (the pole) | ~six months — one sunrise, one sunset a year |
Windows are computed from solar declination versus latitude; refraction, observer height and terrain stretch real sunrises a few days beyond the geometric edges.
How to interpret the result
The most common errors come from using a correct result to answer the wrong geographic question. Keep these points in mind for Polar Day / Night Checker:
- When comparing day length across a year, remember the curve is your latitude's signature: near-equatorial sites hover at twelve hours while high latitudes swing wildly. Choose expectations by latitude, not by calendar folklore.
- Convert solar times to local clock times deliberately: the sun keeps astronomical time, while governments keep political time, and the gap between them is large in many countries. State both when sharing results.
Limits & appropriate use
Solar arithmetic's limits are small but real: the official zenith encodes average refraction, not today's atmosphere; coordinates are rounded to your input's precision; and terrain is absent unless you add height yourself — a mountain rises the sun late and the formulas won't know. Time adds the political layer: zones and DST are human law, and western edges of big zones (Spain, western China) make solar noon wander hours from clock noon. Every output here therefore carries its convention and both clocks, because an unanchored sunrise time is an argument, not a fact.
Lunar and seasonal outputs carry their own gentle limits: phase from the synodic approximation is hours-precise, which outruns every planning need but not ephemeris science; day length is geometric daylight, not sunshine, and clouds belong to climate's department. Escalation is rare and well-defined — astronomical almanacs and ephemerides for science, terrain-aware apps for mountain photography, and the tz database maintainers whenever a government invents a new DST rule at 48 hours' notice, as they delight in doing.
- Science-grade ephemerides → astronomical almanacs/JPL horizons.
- Mountain sunrise/sunset → terrain-aware horizon adjustments.
- Legal daylight definitions → jurisdictional statutes (they vary!).
Data & methodology
The annual daylight chart samples 2025 solar calculations, including zero or 24-hour days at high latitudes; it does not accept an arbitrary date.
For source details, licences and model limitations, see Data Sources and Methodology.
Key terms worth knowing
- Declination
- The sun's latitude-equivalent angle, ±23.44° across the year.
- Equation of time
- The sundial-vs-clock correction from orbit eccentricity and tilt.
Editorial guidance: MapBench explains the method and limitations so the tool can be used as a transparent reference, not as a black-box answer. For legal boundaries, safety-critical routing, surveying, engineering, regulated decisions or official statistics, verify the result with the responsible authority or a qualified professional.
Category: Sun & Moon. Results are intended for everyday analysis and planning unless a page explicitly states otherwise.
Method, assumptions & limits
- This tool’s method
- The annual daylight chart samples 2025 solar calculations, including zero or 24-hour days at high latitudes; it does not accept an arbitrary date.
- Before relying on the answer
- Check the date, location and time zone together. A solar or lunar event is tied to all three, and some events do not occur at high latitudes on a given date.
- What the result cannot establish
- A calculated event assumes the model's horizon and atmospheric conventions. Buildings, terrain and local weather can alter what you observe.
Coverage: Worldwide. Search, basemap and external data requests may use third-party services; browser-based does not mean every operation is offline. Read the source and licence notes, calculation methodology and privacy policy. If a result looks inconsistent, report a correction with the inputs and mode used.
Frequently asked questions
Clear answers about the calculation, accuracy and appropriate use.
Exact civil twilight?
Day-length tools use sunrise/sunset definitions — twilight bands differ.
Are sunrise and solar times exact to what I will see?
Calculated events use astronomical geometry. Terrain, buildings, weather and atmospheric conditions can shift what an observer actually sees.
Does daylight saving change the Sun's position?
No. Daylight saving changes the civil clock label, not solar geometry. Timezone rules affect displayed local time.
Why can polar locations show unusual results?
High latitudes can have days when the Sun does not rise or set, so some solar events legitimately do not occur on a selected date.
What counts as polar day?
The Sun's centre never dips below the horizon for a full 24 hours — including days when it merely skims. The checker uses the geometric definition and says so.
What about twilight during polar night?
Polar night is not all pitch black: near the circles, midday brings hours of civil twilight — a blue noon without a sunrise.
Why do the circles sit at 66.56°?
90° minus Earth's axial tilt (23.44°). The tilt sets the circles, the tropics, and this checker's thresholds.
Does the checker handle the Antarctic?
Yes — southern latitudes mirror the north with seasons flipped: polar day around December, polar night around June.
Refraction and mountains change it?
Yes — real horizons and atmospheric bending add sunrises at the margins. The checker reports the geometric rule; local almanacs fine-tune.
Can the whole winter really lack sunrise?
At the pole, yes — one sunset in September, one sunrise in March. Settlements like Svalbard's live a ~two-month version of it.
Midnight sun versus 24-hour daylight?
Same phenomenon; 'midnight sun' is the friendlier name. Civil twilight swapping in at the edges is the softer variant the checker also flags by latitude.
Where does it never happen?
Everywhere equatorward of the two circles — which is most of the inhabited world, and why visitors find it so strange.
Related tools and resources
The lines: the Arctic Circle and Antarctic Circle; the machinery: Seasons by Latitude; day lengths: the Day Length Calculator.
More free tools
Sources, methodology & editorial trust
- ✓ Browser-first processing where supported
- ✓ External sources are documented
- ✓ No account required for public tools
- ✓ Review data sources
Calculations are documented with their assumptions, limitations and source context rather than presented as unexplained answers.
Reviewed and maintained by Aryan Khan, Founder & Editor of MapBench.
Part of our sun & moon hub
Polar Day / Night Checker sits in the sun & moon cluster, alongside 27 other tools that answer neighbouring questions with different methods or datasets.
You may also need
When this answer is only part of the job, these clusters cover the next step.
Read the guide behind this tool
Chasing Golden Hour: A Photographer's Solar Toolkit — Golden hour is an altitude band, not a fixed clock time. How to plan light with solar tools — windows, horizons and moon phase — instead of guessing.