Coastal Time & Sun Context
Use sunrise/sunset at a coastal location while checking formal tide stations separately.
By Aryan Khan, Founder & Editor · Updated October 2026
For example, where tides are semidiurnal, high water returns every ~12 hours 25 minutes — so today's 9:00 high tide becomes roughly 9:50 tomorrow, marching ~50 minutes later each day with the Moon.
How to use Coastal Time & Sun Context
The Moon pulls the tide, the Sun lights the day — read both clocks together:
Coastal Time & Sun Context gathers what a shore visit runs on — the tide's twice-daily rhythm, the Moon phase driving it, and the sun times framing the day — in one place. Context only: official tide tables remain the authority for heights and exact times.
- 1Set the beach or harbour.
- 2Read sun times for the date.
What people use Coastal Time & Sun Context for
1. Beach-day planning
Sand width, rock pools and safe swimming all ride the tide's phase; light rides the Sun. This page is the pre-check before the Sunrise and Sunset Calculator and the official tide table.
2. Understanding a tide table
Why high tide shifts ~50 minutes daily, why springs follow the full moon — the context that turns a printed table into a system you can sanity-check. Full moons: the Next Full Moon Calculator.
3. Coastal walks and causeways
Tidal causeways and strandings are context failures. Know the rhythm, then verify the day's official times before boots touch sand.
4. Fishing and foraging trips
Feeding windows and exposed beds follow the ebb; moon phase grades the springs and neaps your week will see.
Worked examples
The lunar day is ~24 h 50 min (the Moon orbits while Earth spins), so semidiurnal tides beat every ~12 h 25 min and drift ~50 min later daily — arithmetic you can verify against any week's table.
At new and full moon, Sun and Moon pull together: higher highs, lower lows (springs). At the quarter moons they pull at right angles: gentler neaps. The phase calendar predicts the fortnight's character, not its centimetres.
The context, piece by piece
What this page tells you — and what it deliberately does not.
| Element | What you learn |
|---|---|
| Tide rhythm | ~12 h 25 min semidiurnal beat (some coasts are diurnal or mixed) |
| Moon phase | Where you are in the spring–neap fortnight |
| Sun times | Sunrise, sunset and twilight for the same shore day |
| Not included | Tide heights and minute-exact local times — official tables own those |
Local tide times lag the Moon by a port-specific amount (the 'establishment') shaped by bays and shelves — which is exactly why predictions belong to official tables.
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 Coastal Time & Sun Context:
- 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.
- For photography, plan around sun altitude, not clock time: golden hour is an altitude band, so its clock time migrates with the seasons even at a fixed place — the calculator's windows handle that for you.
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 shared sun workspace computes solar events; it does not retrieve tides. Check an authoritative local tide table separately.
For source details, licences and model limitations, see Data Sources and Methodology.
Key terms worth knowing
- Synodic month
- The 29.53-day new-moon-to-new-moon cycle behind phases.
- Declination
- The sun's latitude-equivalent angle, ±23.44° across the year.
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 shared sun workspace computes solar events; it does not retrieve tides. Check an authoritative local tide table separately.
- 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.
Tide heights?
Not a tide model — use national hydrographic tide tables.
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.
Does it give tide heights?
No — heights and exact local times come from official tide tables for your port, which this page points you toward rather than imitating. Context here, authority there.
Why do tides follow the Moon, not the Sun?
The Moon is far closer, so its tidal pull wins despite its size. The Sun modulates — hence springs at alignment (new/full) and neaps at quarters.
What are spring tides? (Not the season.)
The fortnightly big tides near new and full moon — 'spring' from the old word for leap/rise, unrelated to March.
Are all tides twice-daily?
No — semidiurnal (two a day) dominates the Atlantic; the Gulf of Mexico leans diurnal (one a day); parts of the Pacific mix both. Your coast's type is in its official table.
How late does high tide get each day?
About 50 minutes later per day on semidiurnal coasts, tracking the Moon's ~24 h 50 min day.
Sun times at the coast — why included?
Dawn patrols, golden-hour beach photos and safe returns all hang on the same day's light. One page, whole shore day.
Can I plan a tidal-island visit from this?
Use this for the rhythm, then confirm the exact safe window in the official table for that island — causeway crossings are not a place for estimates.
Moonrise over the sea?
The Moon Position Map and Moonrise pages on this site give the Moon's own schedule — beautiful with an incoming tide.
Related tools and resources
Sun frame: the Sunrise and Sunset Calculator; the driver: the Next Full Moon Calculator and Moonrise and Moonset.
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
Coastal Time & Sun Context 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.