Originally, both the Winter and Summer Olympics occurred on the same year, but a decision in 1986 reversed this, and went into effect beginning in 1994.
On October 14th, 1986, the International Olympic Committee decided to begin to stagger the Winter and Summer Olympics so that there would be an Olympiad every two years. This began with the XVII Winter Games, which were hosted in Lillehammer, Norway in 1994.
From the start of the Winter Olympics in 1924, they had occurred earlier in the same year as the Summer Games.
Upcoming Olympic Games include the 2014 Winter Games to be hosted by Russia and the 2016 Summer Olympiad to be hosted by Brazil.