# sunrisewhen.com

Sunrise, sunset, golden hour, and UV index data for ~146,000 cities worldwide.

## Data

- Calculated with the Python `astral` library (no external API dependency)
- Solar data: Spencer 1971 formula (solar declination)
- Lunar data: Conway algorithm via Julian Date
- Reference system: WGS-84
- Coverage: ~584,000 pages across cities globally

## Key pages

- /[city-slug] – Core sunrise/sunset times
- /[city-slug]/golden-hour – Photography golden hour windows
- /[city-slug]/uv-index – Daily UV index forecast
- /[city-slug]/photography – Photography planning guide per city

## Tools

- /poster/ – "A Year of Light" Astronomical Poster Studio: generate a personalised
  high-resolution (5906×8268 px) poster for any city and year, featuring real solar
  and lunar data. Customisable color palettes, typography (Editorial/Modernist),
  data layers, paper grain finish, special occasion date markers, and optional
  room preview. Orderable as a museum-quality 50×70 cm (20×28 in) matte print,
  shipped worldwide to 20+ countries.