Compute sunrise, sunset, solar noon, and civil/nautical/astronomical twilight times for a coordinate + date. Query: lat (-90..90), lon (-180..180), date (YYYY-MM-DD). All times returned as ISO 8601 UTC. At high latitudes near solstices an event may not occur (polar day/night) — those fields return null and a note is included. dayLengthMinutes is the sunrise→sunset interval.