The winter solstice falls on the 21st in most years, giving the shortest day of the year: under eight hours of daylight in London, around six and a half in Glasgow, and barely five and a half in Lerwick. From that point the days lengthen again, at first by less than a minute a day.
Two bank holidays come out of the 31 days of December 2027 everywhere in the United Kingdom, and a good many workplaces close entirely between Christmas and New Year on days that remain ordinary working days in the count above. The effective break is usually longer than the statutory one.
December 2027 closes the year on the 31st, with Hogmanay in Scotland running into a second bank holiday on 2 January that the rest of the United Kingdom does not get. January then opens a fresh twelve months with its holidays and school terms already fixed.