On June 21st we passed the winter solstice. While both the winter and summer solstices are renowned for Pagan rituals, the solstice is actually an astronomical event.
The winter solstice occurs when the Sun stops setting further north. It then slowly starts setting a little more south each day, moving rapidly as it sets due west at the equinox in September, the slowing to a stop at its furthest point south at the summer solstice in December.
The length of daylight also gradually increases from now until we reach the long summer days of December and January.