Sunrise
Sunrise is the morning horizon event. In the Halo presentation it begins the daylight arc.
Solar noon
Solar noon is the Sun's local meridian passage. It is the exact event that Solar Time names 12:00.
Sunset
Sunset ends the daylight interval and begins the night interval used by the Halo and Byzantine Time.
Golden hour is light, not a fixed hour.
Golden hour is tied to low solar elevation. Its civil-clock time changes with place, date and season, which is why a Solar Reminder can be more useful than a fixed alarm.
Blue hour
Blue hour names a cool low-light interval around dawn or dusk. It is a visual state derived from the Sun, not a standard civil-clock appointment.
Night does not begin all at once.
Civil twilight
The Sun is below the horizon but broad atmospheric light remains clearly present.
Nautical twilight
The sky is much darker, the horizon may remain faintly legible and bright stars become more visible.
Astronomical twilight
The remaining solar contribution continues to fade toward the natural night baseline.
High-latitude days
Some dates have no sunset or no sunrise. SOLAR keeps those states explicit instead of forcing every place into an ordinary sunrise-to-sunset story.