December Solstice

This marks the beginning of winter (in the northern hemisphere) and the beginning of summer (in the southern hemisphere.) The winter solstice is the shortest day of the year, respectively, in the sense that the length of time elapsed between sunrise and sunset on this day is a minimum for the year. Of course, daylight saving time means that the first Sunday in April has 23 hours and the last Sunday in October has 25 hours, but these human meddlings with the calendar and do not correspond to the actual number of daylight hours.

If you live in the southern hemisphere, this is your Summer Solstice, and good cause for celebrating the longest day of the year.