A chart is a viewpoint, not a decorative star field
Date, clock time, latitude, longitude, and timezone context define the observation. ANGIE uses those inputs to place the sky relative to the observer’s horizon. That means the same calendar date can produce meaningfully different local views at different times or places.
Sources: U.S. Naval Observatory — Computing Altitude and Azimuth · NASA/JPL — Horizons System Manual
The chart and the object are separate
The calculated render is the artwork. A poster, digital file, garment, or other supported product is a carrier for that render. This separation lets one verified moment survive across multiple layouts without pretending the astronomy changed.
Birth charts are only one use
Births are common because they come with a recorded time and place, but the same system works for meetings, weddings, departures, discoveries, performances, memorials, or any other moment you can define.