“Sunrise” sounds like a simple observation: the Sun shows up. In published tables and calculators, it is a standardized geometric event — so two careful sources can match even when your local hill blocks the view.
The Official Definition
Most modern calculators (including Sunset Sunrise Today) treat sunrise/sunset as the moment when the Sun’s apparent upper limb is on the horizon for a sea-level observer, using a solar zenith angle of 90.833°.
That 90.833° figure bundles two corrections:
- Solar radius (~0.267°) — we care about the upper edge, not the center
- Average atmospheric refraction (~0.567°) — air bends sunlight so the Sun appears slightly higher than its geometric position
Without those corrections, tables would disagree with what people perceive on an open horizon.
Apparent vs Geometric Sun
Because of refraction, you can still see the Sun when it is geometrically below the horizon. That is why sunrise occurs a little earlier — and sunset a little later — than a vacuum-Earth model would predict. It is also a major reason equinox days usually exceed 12 hours of daylight.
What Calculators Assume
Standard sunrise/sunset times assume:
- A flat horizon (no mountains or skyline)
- Average refraction (actual refraction varies with temperature and pressure)
- Observer near sea level (altitude changes the geometry slightly)
If you watch sunrise from a valley, the Sun may clear the ridge minutes after the tabulated sunrise. The table is not “wrong”; it answered a different question.
Sunrise vs Twilight Definitions
| Event | Solar depression / zenith idea |
|---|---|
| Official sunrise/sunset | Upper limb on horizon (90.833° zenith) |
| Civil twilight ends/begins | Sun at −6° |
| Nautical | Sun at −12° |
| Astronomical | Sun at −18° |
Photography terms like golden hour (+6° to −4°) and blue hour (−4° to −8°) sit alongside these scientific bands but are creative conventions. See Dawn vs Dusk and the Twilight Calculator.
DST, Time Zones, and “Correct” Local Time
Algorithms compute the instant in universal time, then format it in the location’s IANA timezone (for example `Asia/Dhaka` or `America/New_York`). Daylight Saving Time shifts the clock label, not the sky. That is why solar noon can sit near 1:00 PM in summer clock time.
Why This Site’s Times Match Professional Standards
We use NOAA/Meeus-style solar position equations shared across reputable astronomy tools: solar declination, equation of time, and zenith-based event solving. The goal is consistency with scientific convention — then city pages add forecasts and monthly tables so the definition becomes useful day to day.
Open the Sun Calculator hub for the full toolkit, or jump to any city for labeled sunrise and sunset under this definition.