The next astronomical phenomenon in 2015 is winter solstice, which occurs on December. It is the shortest day of the year and the longest night. It is an important day in many religions and cultures. For the Northern Hemisphere, it occurs every year around December 25, which is also the date of Christmas. However, planets like Saturn don't have annual equinoxes in the sense of Earth years. They are more random to our calendar, and the next equinox on Saturn won't occur until 2024. The last one was in 2009.