Read about it here.
Whether or not it is linked to the winter solstice, the festival of Hogmanay has little to do with Christianity. The very name points to profoundly pagan origins and its meaning is lost in antiquity. Any suggestion that it means "all men drink like hogs" is Sassenach slander.
Hogmanay is about darkness. It is a ceremony based on the three "Ds": the dark, the devil and the dram. That is why a proper Scottish New Year does not start until midnight. The previous hours are spent lining the stomach with heavy food and non-alcoholic beverages, such as wine, so that the innards are fortified against the onslaught of the whisky bottle.
Then midnight strikes: the blackest hour, when the forces of darkness dominate. How to repel them? Strong drink, strong men, who go in procession from house to house, bearing bottles of whisky and lumps of coal. The darkest-visaged is chosen to put the first foot across the threshold, so that, however black the features, it will be a friendly first foot — and not Satan. The first foot's lump of coal is a harmless addition to the domestic hearth, not fuel borrowed from the infernal furnaces.
So Hogmanay may have some tenuous links with Christianity. It appears to draw from the two elements which the Scots always found most inspiring: hell fire and the devil. In the spirit fired up from eternal conflict, the Scots spend the first six hours or so of the New Year keeping the de'il at bay with their equivalent of a crucifix and garlic: whisky. The word "whisky" is a corruption of the Gaelic for the water of life: its vital function on New Year's morn.
After a rest for sleep and rehydration, Hogmanay resumes around lunchtime on January 1, just to ensure that the devil has been kept off the premises. In recent years, January 2 has also become a virtual holiday in Scotland and one can understand why. It is not actually known as liver-function resumption day, but that is the general idea.
Happy Hogmanay, y'all!!!