Sunrise, Sunset and Golden Hour

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civil nautical astronomical twilight times

Civil, nautical and astronomical twilight: times and how long they last

Between sunset and full night there are three stages, defined by how far the Sun sits below the horizon. Each serves a purpose: streets, navigation and astronomy.

The three U.S. Naval Observatory definitions

The U.S. Naval Observatory (USNO) defines civil twilight as the interval in which the center of the Sun is within 6 degrees below the horizon: before it begins in the morning and after it ends in the evening, artificial light is normally needed for outdoor activity. Nautical goes to 12 degrees: the horizon is still visible at sea, which is when navigators take star sights. Astronomical goes to 18 degrees: after it the Sun's scattered light is weaker than that of stars and other natural sources. The USNO cautions that the actual light level depends on the atmosphere, cloud cover and the visible horizon.
Duration depends on latitude, because the Sun descends at a shallower angle away from the equator. On December 21, 2026 in São Paulo sunrise is at 05:17 and the three twilights begin at 04:52, 04:21 and 03:49, so they last 25, 56 and 88 minutes. On June 21, near the equator in Quito, they last 23, 49 and 75; in New York, 33, 76 and 127. In London on December 21 it is 40, 84 and 124 minutes before the 08:04 sunrise. The nearer the pole, the longer, up to the point where twilight stops ending.
That happens in London, at 51.5 degrees north, on June 21, 2026. The Sun sets at 21:22, civil twilight ends at 22:09 and nautical at 23:24, but the Sun never goes below -18 degrees: there is no astronomical twilight or astronomical night that date. In Reykjavik, at 64.1 degrees, the Sun gets no more than 2.4 degrees below the horizon, so not even civil twilight ends. In each case the tool states that the Sun "does not go below" that altitude, instead of leaving the time blank with no explanation.

Twilights as computed by the tool

São Paulo, 21/12/2026

Input: São Paulo, 21/12/2026, manhã
Expected output: 03:49, 04:21, 04:52, nascer 05:17

Astronomical, nautical, civil: 88, 56 and 25 minutes before sunrise.

São Paulo, evening

Input: São Paulo, 21/12/2026, tarde
Expected output: pôr 18:52, 19:18, 19:48, 20:20

Civil ends at 19:18, nautical at 19:48 and astronomical at 20:20.

Quito at the June solstice

Input: Quito, 21/06/2026
Expected output: 23, 49 e 75 minutos

Short twilights near the equator.

London at the June solstice

Input: Londres, 21/06/2026
Expected output: civil 03:55 a 22:09, náutico 02:41 a 23:24, astronômico: nenhum

The Sun never goes below -18°.

Reykjavik at the June solstice

Input: Reykjavik, 21/06/2026
Expected output: nenhum dos três; Sol mínimo -2,4°

Sunset at 00:04 (+1 day).

Full tool FAQ

How do I find out when the sun rises and sets in my city?

Pick the city and date above. The time comes from the Sun's position calculated for the city's coordinates, in the city's time zone, with daylight saving time where it applies. In São Paulo on December 21, 2026 the Sun rises at 05:17 and sets at 18:52; on June 21, 2026, at 06:48 and 17:29.

What is golden hour and when does it happen?

What is blue hour?

What is the difference between civil, nautical and astronomical twilight?

Why does sunset time change so much through the year?

Is the longest day also the day the Sun rises earliest?

Why do some times show +1 day?

Are there midnight sun and polar night? What does the tool show?

Why does the time differ by a minute or two from my phone app?

Does it work offline and does it handle daylight saving time?

Frequently asked questions

When does true night begin?

When the Sun passes 18 degrees below the horizon, at the end of astronomical twilight. In São Paulo on December 21, 2026 that is 20:20, nearly an hour and a half after the 18:52 sunset.

What is astronomical twilight used for?

To know when the sky becomes dark enough to observe faint objects such as galaxies and the Milky Way. That is why the meteor calendar's night analysis uses the same 18-degree limit.

Why is twilight longer far from the equator?

Because the Sun descends at a slant, and takes longer to cover the same degrees below the horizon. In New York civil twilight lasts 33 minutes in June, against 23 in Quito.

Next steps

The three U.S. Naval Observatory definitions

The U.S. Naval Observatory (USNO) defines civil twilight as the interval in which the center of the Sun is within 6 degrees below the horizon: before it begins in the morning and after it ends in the evening, artificial light is normally needed for outdoor activity. Nautical goes to 12 degrees: the horizon is still visible at sea, which is when navigators take star sights. Astronomical goes to 18 degrees: after it the Sun's scattered light is weaker than that of stars and other natural sources. The USNO cautions that the actual light level depends on the atmosphere, cloud cover and the visible horizon.

Duration depends on latitude, because the Sun descends at a shallower angle away from the equator. On December 21, 2026 in São Paulo sunrise is at 05:17 and the three twilights begin at 04:52, 04:21 and 03:49, so they last 25, 56 and 88 minutes. On June 21, near the equator in Quito, they last 23, 49 and 75; in New York, 33, 76 and 127. In London on December 21 it is 40, 84 and 124 minutes before the 08:04 sunrise. The nearer the pole, the longer, up to the point where twilight stops ending.

That happens in London, at 51.5 degrees north, on June 21, 2026. The Sun sets at 21:22, civil twilight ends at 22:09 and nautical at 23:24, but the Sun never goes below -18 degrees: there is no astronomical twilight or astronomical night that date. In Reykjavik, at 64.1 degrees, the Sun gets no more than 2.4 degrees below the horizon, so not even civil twilight ends. In each case the tool states that the Sun "does not go below" that altitude, instead of leaving the time blank with no explanation.

Twilights as computed by the tool

São Paulo, 21/12/2026

Input: São Paulo, 21/12/2026, manhã
Expected output: 03:49, 04:21, 04:52, nascer 05:17

Astronomical, nautical, civil: 88, 56 and 25 minutes before sunrise.

São Paulo, evening

Input: São Paulo, 21/12/2026, tarde
Expected output: pôr 18:52, 19:18, 19:48, 20:20

Civil ends at 19:18, nautical at 19:48 and astronomical at 20:20.

Quito at the June solstice

Input: Quito, 21/06/2026
Expected output: 23, 49 e 75 minutos

Short twilights near the equator.

London at the June solstice

Input: Londres, 21/06/2026
Expected output: civil 03:55 a 22:09, náutico 02:41 a 23:24, astronômico: nenhum

The Sun never goes below -18°.

Reykjavik at the June solstice

Input: Reykjavik, 21/06/2026
Expected output: nenhum dos três; Sol mínimo -2,4°

Sunset at 00:04 (+1 day).

Full tool FAQ

How do I find out when the sun rises and sets in my city?

What is golden hour and when does it happen?

What is blue hour?

What is the difference between civil, nautical and astronomical twilight?

Why does sunset time change so much through the year?

Is the longest day also the day the Sun rises earliest?

Why do some times show +1 day?

Are there midnight sun and polar night? What does the tool show?

Why does the time differ by a minute or two from my phone app?

Does it work offline and does it handle daylight saving time?

Frequently asked questions

When does true night begin?

When the Sun passes 18 degrees below the horizon, at the end of astronomical twilight. In São Paulo on December 21, 2026 that is 20:20, nearly an hour and a half after the 18:52 sunset.

What is astronomical twilight used for?

To know when the sky becomes dark enough to observe faint objects such as galaxies and the Milky Way. That is why the meteor calendar's night analysis uses the same 18-degree limit.

Why is twilight longer far from the equator?

Because the Sun descends at a slant, and takes longer to cover the same degrees below the horizon. In New York civil twilight lasts 33 minutes in June, against 23 in Quito.