A real shadow in an imagined courtyard
Only the vertical gnomon’s shadow is calculated. Its bearing is opposite the Sun and its length on a horizontal plane is height divided by tan(solar altitude). The trees, water, stonework and surrounding light form an illustration, not a surveyed building or a complete physical lighting simulation.
The city supplies a place and a clock
Each city uses listed representative coordinates and an IANA time zone. Local time is converted to UTC with historical zone rules. Skipped clock times are rejected; repeated times need an explicit first or second occurrence. Dates are supported from 1901 to 2099, with zone data supplied by the browser.
At the edge of daylight
Astronomy Engine 2.1.19 computes the topocentric geometric Sun centre without atmospheric refraction. At or below zero altitude, the scene shows night and no solar shadow. Below 3° the near-horizon warning appears; long shadows are visually clipped to the courtyard while the numerical length remains visible. Terrain, weather and refraction can change what you see outdoors.