The first (and only!) sunset^{1} this year at Amundsen–Scott South Pole Station in Antarctica occurs on March 22 at 0615 UTC (using “astronomer’s time” as time zone has no meaning so close to the South Pole).

The year’s first and only end of **civil twilight** (when the geometric center of the Sun lies 6° below the horizon) occurs on April 4 at 1153 UTC. That’s 13^{d}05^{h}38^{m} after sunset.

The year’s first and only end of **nautical twilight** (when the geometric center of the Sun lies 12° below the horizon) occurs on April 21 at 0409 UTC. That’s 16^{d}16^{h}16^{m} after the end of civil twilight.

The year’s first and only end of **astronomical twilight** (when the geometric center of the Sun lies 18° below the horizon) occurs on May 11 at 0521 UTC. That’s 20^{d}01^{h}12^{m} after the end of nautical twilight, and 49^{d}23^{h}06^{m} after sunset. That’s one heck of a long twilight!

**Night lasts from May 11 at 0521 UTC until astronomical twilight begins on July 31 at 1916 UTC. A duration of 81 ^{d}13^{h}55^{m}.**

Nautical twilight begins on August 21 at 0024 UTC. That’s 20^{d}05^{h}08^{m} after the beginning of astronomical twilight.

Civil twilight begins on September 6 at 2121 UTC. That’s 16^{d}20^{h}57^{m} after the beginning of nautical twilight.

The first and only sunrise of the year occurs on September 20 at 0945 UTC. “Morning” twilight lasts a total of 50^{d}14^{h}29^{m}.

The Sun remains above the horizon continuously until sunset on March 22, 2025 at 1100 UTC. Daylight “hours” last 183^{d}01^{h}15^{m}.

Strange place!

^{1}**Sunrise and sunset.** For computational purposes, sunrise or sunset is defined to occur when the geometric zenith distance of the center of the Sun is 90.8333 degrees. That is, the center of the Sun is geometrically 50 arcminutes below a horizontal plane. For an observer at sea level with a level, unobstructed horizon, under average atmospheric conditions, the upper limb of the Sun will then appear to be tangent to the horizon. The 50-arcminute geometric depression of the Sun’s center used for the computations is obtained by adding the average apparent radius of the Sun (16 arcminutes) to the average amount of atmospheric refraction at the horizon (34 arcminutes).

[Reference: https://aa.usno.navy.mil/faq/RST_defs, but see here:

https://digitalcommons.mtu.edu/etdr/697/]

**Note**: SkySafari 6 Pro, Version 6.8.2 (6820) for MacOS was used to determine these dates and times. The location coordinates used for Amundsen–Scott South Pole Station were 89° 58′ 59.9″ S, 139° 16′ 01.2″ E, 2835 m.

**Fun Fact**: Did you know that there is a seismic station near the south pole, and that it has been operating since 1957?