Starry Memory

Night length and darkness calendar for Rotterdam

Use the free local tool

This page provides a result prefilled with the place and coordinates. The calculations and phone gyroscope work without an order; the HD poster remains optional. Open the twelve-month Rotterdam calendar

Compare all twelve months and find the longest local observing windows

A good month for stargazing is not the same everywhere. Latitude changes the seasonal balance between daylight and night. The table below estimates day and night length around the middle of every month for Rotterdam, using a flat astronomical horizon and explaining the limits of twilight, weather and terrain.

Why choose Starry Memory

Twelve local estimates — Monthly night duration ranges from 7 h 33 to 16 h 27 in the flat-horizon model.
GPS · IANA reference — Exact reference: South Holland, 51.9225° N, 4.4792° E, Europe/Amsterdam.
Free tool — The city-specific tool works free in the browser and does not create an order.
Transparent limits — Weather, light pollution and local obstructions are stated as limits instead of being hidden.

Rotterdam's changing light is read month by month, using its actual seasonal range rather than generic observing advice. Its verifiable starting point is GeoNames 2747891, 51.9225° N, 4.4792° E, in timezone Europe/Amsterdam.

Twelve monthly light estimates for Rotterdam

The following pairs are approximate daylight / night duration around the 15th of each month: January: 8 h 02 / 15 h 58; February: 9 h 40 / 14 h 20; March: 11 h 31 / 12 h 29; April: 13 h 38 / 10 h 22; May: 15 h 26 / 8 h 34; June: 16 h 27 / 7 h 33; July: 16 h 02 / 7 h 58; August: 14 h 26 / 9 h 34; September: 12 h 23 / 11 h 37; October: 10 h 20 / 13 h 40; November: 8 h 29 / 15 h 31; December: 7 h 33 / 16 h 27. The longest estimated night in this model is December at 16 h 27; the shortest is June at 7 h 33. “Night” here is the complement of daylight on a flat horizon. Civil, nautical and astronomical twilight are not interchangeable, and weather is not predicted by this table.

Rotterdam's verifiable local record

Calculation identity: GeoNames 2747891 · city Rotterdam · region South Holland · country Netherlands · national selection rank 1 · reference population 868,135 · source elevation —. Spatial fingerprint: latitude 51.92250 · longitude 4.47917 · north hemisphere · timezone Europe/Amsterdam · celestial-pole altitude 51.9°. Seasonal signature: longest night in December, 16 h 27 · shortest night in June, 7 h 33 · range 8.90 hours. Meridian star markers: Ursa Major 85.9° * · Perseus 83.1° * · Cassiopeia 81.9° * · Auriga 80.1° * · Cygnus 78.1° * · Draco 76.9° *. Nearby catalogue cities: The Hague 21 km · Breda 43 km · Utrecht 48 km. First regional eclipse shortlist: 2027-02-20 Penumbral lunar eclipse 23:14 UTC · 2027-08-02 Total solar eclipse 10:07 UTC · 2028-01-12 Partial lunar eclipse 04:14 UTC. Together these values form the local evidence record for the “night calendar” page; they change with place and remain separate from real weather.

Rotterdam compared with nearby catalogue cities

1. Rotterdam → The Hague: 21.1 km · Δlat +0.154° · Δlon -0.181° · Δpole +0.2° · timezone Europe/Amsterdam = Europe/Amsterdam · longest night December 16 h 29 | 2. Rotterdam → Breda: 42.6 km · Δlat -0.336° · Δlon +0.297° · Δpole -0.3° · timezone Europe/Amsterdam = Europe/Amsterdam · longest night December 16 h 23 | 3. Rotterdam → Utrecht: 47.8 km · Δlat +0.168° · Δlon +0.643° · Δpole +0.2° · timezone Europe/Amsterdam = Europe/Amsterdam · longest night December 16 h 29. Monthly night comparison with the nearest catalogue reference — January: Rotterdam 15 h 58 / The Hague 15 h 59 / Δ -0.02 h · February: Rotterdam 14 h 20 / The Hague 14 h 21 / Δ -0.01 h · March: Rotterdam 12 h 29 / The Hague 12 h 29 / Δ +0.00 h · April: Rotterdam 10 h 22 / The Hague 10 h 22 / Δ +0.01 h · May: Rotterdam 8 h 34 / The Hague 8 h 33 / Δ +0.02 h · June: Rotterdam 7 h 33 / The Hague 7 h 31 / Δ +0.03 h · July: Rotterdam 7 h 58 / The Hague 7 h 57 / Δ +0.02 h · August: Rotterdam 9 h 34 / The Hague 9 h 33 / Δ +0.02 h · September: Rotterdam 11 h 37 / The Hague 11 h 37 / Δ +0.00 h · October: Rotterdam 13 h 40 / The Hague 13 h 40 / Δ -0.01 h · November: Rotterdam 15 h 31 / The Hague 15 h 32 / Δ -0.02 h · December: Rotterdam 16 h 27 / The Hague 16 h 29 / Δ -0.03 h. For the night calendar, north-south movement is the primary signal: compare Rotterdam's seasonal range with the numbered maximum nights of its neighbours.

The astronomical fingerprint of Rotterdam

Rotterdam is represented by 51.9225° N, 4.4792° E, in South Holland, using the IANA zone Europe/Amsterdam. This is a high-latitude viewpoint: the relevant celestial pole stands about 51.9° above its horizon. GeoNames record 2747891 supplies the geographic reference; its population field is 868,135 and is used for catalogue selection, not presented as a live census. No source elevation is used, so a flat horizon remains the transparent default.

Latitude-screened constellations for Rotterdam

Each entry below gives an approximate maximum altitude at meridian transit and a practical season; an asterisk means circumpolar in this simplified centroid model: Ursa Major: 85.9°, all year *; Perseus: 83.1°, all year *; Cassiopeia: 81.9°, all year *; Auriga: 80.1°, all year *; Cygnus: 78.1°, all year *; Draco: 76.9°, all year *; Cepheus: 71.9°, all year *; Ursa Minor: 64.9°, all year *; Andromeda: 76.1°, autumn; Lyra: 74.1°, summer; Boötes: 68.1°, spring; Gemini: 60.1°, winter; Taurus: 56.1°, winter; Leo: 53.1°, spring. This is a planning guide, not a promise that every star will be visible from a bright street. Date, hour, local obstructions and light pollution still matter. The live sky tool performs the date-specific projection that a static latitude table cannot.

What the calculation does — and does not claim

Coordinates, date and local time feed the same astronomical workflow used by the poster. The HYG catalogue provides star entries, while Astronomy Engine calculates moving bodies. The page does not claim that city-centre coordinates equal a hospital, venue or home: selecting an autocomplete suggestion replaces the shortcut with that location. It also separates astronomical geometry from weather and light pollution, so a correct map never becomes a claim that the ground-level sky was cloudless.

Free gyroscope first, optional poster second

On a compatible phone, the gyroscope turns the calculated sky into a movable window: tilt and rotate to explore, with star names shown beside key points. That experience is free. If a date deserves a keepsake, the same place can continue into the editor. The protected preview remains watermarked before payment; the €3.99 purchase unlocks the 4960 × 7016 px, 300 DPI file. Physical formats appear only when availability, delivery supplement and timing can be checked for the destination. The HD file is charged once at €3.99.

Frequently asked questions

Is night length the same as astronomical darkness?

No. The table shows 24 hours minus estimated daylight. In Rotterdam, twilight shortens fully dark conditions, especially near the longest days.

Can I replace the centre of Rotterdam with an exact address?

Yes. Choose the intended autocomplete suggestion; its coordinates replace the city shortcut. Unselected free text is never silently sent to a default city.

Is the Rotterdam tool free?

Yes. The local calculation, tables and gyroscope exploration can be used without payment. Only the unlocked HD poster is paid.

Does this guarantee clear-sky visibility?

No. The calculations describe geometry. Cloud, terrain, buildings and light pollution can change what a person sees from the ground.

Do I have to buy a poster?

No. The tool stands on its own. If wanted, the watermark-free 4960 × 7016 px, 300 DPI file costs €3.99. The HD file is charged once at €3.99.

Open the twelve-month Rotterdam calendar