The Winter solstice
The Sun reaches its furthest point south today, 21 December.
At 1044 UTC today, 21 December, the Sun reaches its furthest southern extremity of 23º26.1'. Astronomically, this - the shortest day - is the start of Winter but, meteorologically, Winter comprises the months of December, January and February.
The Sun will return to the northern hemisphere at the Vernal equinox - 1028 UTC on 20 March 2017. It will reach the furthest north at the Summer solstice - 0424 UTC on 21 June 2017.
This year is a particularly long one, including both a leap day (29 February) and a leap second, due after 23:59:59 on 31 December. The leap day accounts for the Earth taking ~365.25 days to orbit the Sun - this keeps the seasons consistent year-on-year forever. The leap second accounts for the slowing of Earth's own rotation compared with International Atomic Time (TAI)'s atomic standard, to which it was synchronised in 1972. On 1 January 2017, the difference between Coordinated Universal Time (UTC) and TAI will be 36 seconds.
Further details from the link below . .