What do we mean by the shortest day?

The shortest day, winter solstice and midwinter are the colloquial terms used to describe the 24 hours around an annual astronomical event which occurs around the 22nd December. The shortest day marks the point when the days start to get longer and the nights shorter, and has profound cultural meaning around the world and throughout history. The cultural significance varies, but generally refers to a time of rebirth and renewal and is celebrated with festivals and rituals.

The astronomical event of the solstice occurs when the angle of the Sun to an observer is at its greatest, for an observer in a given hemisphere. For the Northern hemisphere this will be when the Sun is at it's southern most position, and for an observer in the Southern hemisphere the northern most, see Figure 1.

The opposite of the winter solstice is the summer solstice and occurs around the 22nd June, and marks the point when the days are longest and nights shortest.

Timings for the summer and winter solstices are given in Table 1, summarised from the US Naval Observatory page at http://aa.usno.navy.mil/data/docs/EarthSeasons.php

Winter Solstice
Figure 1: Winter solstice as seen by observer in Northern Hemisphere.

Related links

Yahoo! News: Druids, pagans mark shortest day of year (22/12/2009)
Article about celebrations at Stonehenge for the winter solstice 2009.
Shropshire Star: UFO sighting linked to shortest day (07/01/2009)
An article from the Shropshire Star about the shortest day being linked to an increase in UFO activity.
BBC News: Hundreds celebrate shortest day (21/12/2008)
An article from BBC News about the celebrations at Stonehenge in 2008.
Table 1: Solstice times from 2000-2020
2000 June 21 01:48 December 21 13:37
2001 June 21 07:38 December 21 19:21
2002 June 21 13:24 December 22 01:14
2003 June 21 19:10 December 22 07:04
2004 June 21 00:57 December 21 12:42
2005 June 21 06:46 December 21 18:35
2006 June 21 12:26 December 22 00:22
2007 June 21 18:06 December 22 06:08
2008 June 20 23:59 December 21 12:04
2009 June 21 05:45 December 21 17:47
2010 June 21 11:28 December 21 23:38
2011 June 21 17:16 December 22 05:30
2012 June 20 23:09 December 21 11:11
2013 June 21 05:04 December 21 17:11
2014 June 21 10:51 December 21 23:03
2015 June 21 16:38 December 22 04:48
2016 June 20 22:34 December 21 10:44
2017 June 21 04:24 December 21 16:28
2018 June 21 10:07 December 21 22:22
2019 June 21 15:54 December 21 04:19
2020 June 21 21:43 December 21 10:02