Lets start at the beginning..
The Earth orbits around the Sun every 365 days, in a plane called the ecliptic plane. Whilst orbiting the Sun, every 24 hours the Earth also rotates around a central axis. The catch is that the rotation axis of the Earth is not perpendicular to the ecliptic plane - the Earth’s axis of rotation is slightly tilted. Consequently, either the Northern or the Southern hemisphere will be tilted slightly towards the Sun, whilst the opposite hemisphere is tilted slightly away. Therefore, the hemisphere that is tilted towards the Sun experiences summer, and the other winter. During spring and autumn, the Earth’s rotational axis is almost perpendicular to a line drawn between itself and the Sun. This means that day and night will be the same length, and both hemispheres receive an equal amount of sunlight.
Since the Earth is tilted, one of the Poles is directed towards the sun (during its respective hemisphere’s summer), and the other Pole is tilted away from the Sun. The sunward facing side of Earth has day, and the side that faces away from the Sun is cast in shadow, and experiences night. Because of the Earth's tilt, one of the poles will constantly be exposed to the Sun, even though the Earth is rotating through it’s day and night cycle. This pole will experience constant daylight. Naturally, the opposite pole will be cast in shadow during this entire time, and will experience prolonged night. As the Earth moves to the opposite side of the sun, the Earth’s shadow falls in such a way that the opposite pole is now shrouded in darkness, and the scenario is reversed.
The further away one gets from the equator, the more pronounced the seasons get, especially with regards to day length. This can been seen even more so in the polar regions, where summer heralds 24-hour days and winter brings 24-hour nights. At SANAE IV, located at 71°S, this means approximately 3 months of full sunshine in summer and 3 months with no sunrise in winter.
Midwinter is also known as the winter solstice. In the Southern Hemisphere this is the Northern Solstice - the time at which the sun is at its northernmost point in the sky. A hemisphere's winter solstice occurs on the shortest day and longest night of the year, when the sun's daily maximum elevation in the sky is the lowest. This usually hapens on 20 - 21 June each year, depending on whether it is a leap year or not. Since this day announces the turn of the season, the prospect of the sun's return, and also the middle of the year, it is of no surprise then that the solstices have been much more celebrated at the high latitudes.
Midwinter celebrations are a long-standing Antarctic tradition, and at SANAE we are all for traditions. Some of the highlights include the Midwinter greetings exchanged by the different bases on Antarctica and accompanying islands, and then offcourse the Midwinter dinner. This generally consists of a ten-course meal prepared by the team members. Everyone gets dressed up in their fanciest outfit and joins the rest in the bar where we had the tables set up - with tablecloths and candles and everything.
So some awesome scenery, champagne, lots of food and a Monster or two later, it turned out to be quite the memorable evening..
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