Sunlight‑Based Terms for Times of Day

The transition from day to night (and vice versa) is divided into several phases based on the Sun's position relative to the horizon. While we often use words like "dusk" and "twilight" interchangeably in casual conversation, they have precise astronomical and poetic meanings.

Night - The Sun is more than 18° below the horizon; no scattered sunlight reaches the lower atmosphere.

Astronomical Twilight - The Sun is 18° to 12° below the horizon.

• Astronomical dawn — the moment the Sun reaches 18° below the horizon in the morning.

• Astronomical twilight (morning) — faint light appears, but most people still perceive full darkness.

• Astronomical twilight (evening) — faint light persists after sunset.

• Astronomical dusk — the moment the Sun sinks past 18° below the horizon in the evening.

Nautical Twilight - The Sun is 12° to 6° below the horizon.

• Nautical dawn — Sun reaches 12° below the horizon; horizon becomes visible.

• Nautical twilight (morning) — sailors historically used this light to see both stars and the horizon.

• Nautical twilight (evening) — horizon still visible but dim.

• Nautical dusk — Sun reaches 12° below the horizon; horizon visibility fades.

Civil Twilight - The Sun is 6° below the horizon up to the horizon.

• Civil dawn — Sun is 6° below the horizon; enough light for many outdoor activities.

• Civil twilight (morning) — brightening sky before sunrise.

• Civil twilight (evening) — lingering light after sunset.

• Civil dusk — Sun reaches 6° below the horizon; artificial light usually becomes necessary.

Sunrise & Sunset - The Sun crosses the horizon.

• Sunrise — the upper limb of the Sun appears.

• Sunset — the upper limb of the Sun disappears.

Daylight - The Sun is above the horizon.

• Early morning — shortly after sunrise.

• Morning — increasing sunlight.

• Midday / Noon — Sun at its highest point.

• Afternoon — declining but strong sunlight.

• Late afternoon — warm, angled light.

• Golden hour — warm, low-angle sunlight shortly after sunrise or before sunset.

• Blue hour — cool-toned light just before sunrise or after sunset, overlapping civil twilight.

Dawn & Dusk are umbrella terms.

• Dawn — the entire transition from night to sunrise (all twilight phases).

• Dusk — the entire transition from sunset to night (all twilight phases).

Deep Night occurs after astronomical dusk and before astronomical dawn.

• Night — full darkness.

• Midnight — the midpoint of the night (civil time, not astronomical).