This year, 2020, winter solstice happens at 9:43 am NZST on Sunday the 21st of June. This is the moment when the sun reaches it’s furtherest point north of the equator. So, from today the days will slowly start to get longer and the nights shorter as we head towards the spring equinox in September.
Of course, in the northern hemisphere this moment marks the mid-summer solstice and the solstice happens at the same time world-wide. It is completely independent of phases of the moon, the rising or setting of stars above the horizon or any other celestial events. While it normally happens on June the 21st each year it can occur on the 20th and also (rarely) on the 22nd.
The Earth follows an elliptical orbit around the Sun and is at it’s furtherest distance about two weeks after the southern winter solstice, some 5 million kilometres more distant than in January. On July the 4th 2020 at 11:34 am NZST the distance between the centre of the Earth and the centre of the sun will be 152,095,295 km (94,507,635 mi).