In bygone days the winter solstice conjured up all sorts of wild myths and beliefs among the Celtic peoples of Britain and other peoples throughout Europe. In the northern parts of Europe, there were vast forests with remote places. The isolated groups that lived in such areas were susceptible to all sorts of suspicions and loved to listen to tales told by wandering bards or other such story tellers.
The surrounding Ecosystems of their realm were hosts to many types of beliefs and the seasons often changed the dweller's concept of the forest areas in magical and mystical ways. Winter being viewed in a completely different way to summer. Each season was celebrated and each solstice was too.
The solstice is celebrated in Britain and has been for thousands of years. There are suspected religious festivals and various stone rings aligned to celebrate such things. We have a summer and winter solstice across the planet and the solstice is opposite either side of the Earth's equator.
Therefore, when Britain, a northern hemisphere country, celebrates its winter solstice on the 21st of December, a southern hemisphere country like Australia will celebrate its summer solstice.