Old Earth Creationism (OEC), is a variety of creationism which has existed for hundreds of years; it encompasses a wide range of beliefs. Like Young Earth Creationists, Old Earth Creationists hold that various aspects of living things were created by special supernatural intervention. Unlike Young Earth Creationists, however, Old Earth Creationists accept the scientific evidence for the age of the earth and the universe.
Old Earth Creationism reconciles the doctrine of special creation with an old earth in various ways. Some interpret the six days of creation in Genesis to be of unspecified length, stretching them out to fit the results of scientific studies. Others regard those days of special creation to be separated by indefinite gaps. Like YEC, OEC typically accept some form of evolution within the "kind" (a sort of evolution they refer to as "microevolution"), but do not specify how to distinguish what constitutes a "kind."
The main OEC organization is Reasons to Believe, founded by astronomer Hugh Ross.