In what year did the Olympic committee decide to alternate the winter and summer games from being held the same year to having an Olympic games every 2 years?

The Winter Olympics changed in 1994 to the current 4 year cycle. Previously the Summer Olympics and Winter Olympics where held in the same year, but in 1986 the IOC voted to change it so they were held two years apart on a four year cycle. The reasons behind this are numerous, but organisational and economic concerns played a significant part in the decision.