"Gimme that old time religion
Gimme that old time religion
Gimme that old time religion
It's good enough for me!"
The old spiritual conjures up images of rural churches in early 20th century America, and that is precisely the issue. The "old-time" religion and the ideas and images connected to it are not that old. Many Christians long for the "old-time religion" that goes all the way back--eons and light years--to the late 19th century. The hymn, "Give Me That Old-Time Religion" was adapted from an African-American spiritual in 1889 and published in 1891 by Charlie Tillman. The old time religion is not so aged. There were about 1900 years of Christianity before it.
Similarly, Christian fundamentalists are often viewed as defenders of traditional Christian values and "conservers" of old ways of faith. In many ways, they were (and are) precisely the opposite. In 1925, fundamentalists were dealt a significant blow at the Scopes Monkey Trial in Dayton, Tennessee. People felt that Clarence Darrow and William Jennings Bryan's exchange put fundamentalist Christianity in a bad light. So, during the 1930s, 1940s and 1950s, the Fightin' Fundies went underground. They did not rely on old methods; they used new methods to build their base. They created summer camps, meetings, and conferences. They separated from secular society and created their own colleges and other schools. They used mass-produced pamphlets and papers to spread their ideas. They turned to the newfangled radio and made use of the new airwaves. Charles Fuller's Old Fashioned Revival Hour converted thousands to fundamentalist Christianity by appealing to listeners with intimacy, family, conservatism, and "old-time" comfort during the Depression and WWII (1). The use of new technology has remained at the forefront of fundamentalism through the mass production of written material, television, movies, and the internet.
Despite their call for old-time comfort, their theology had a "new" feel as well. Dispensational premillennialism ("Rapture Theology" or "Antichrist Theology") was not popularized until the mid-1800's. This fit their world view well, because they were separating from the Godless society that they saw around them. Dispensational Premillennialists saw the world in decline and themselves as a persecuted group. World War II seemed to bring some fulfillment of biblical prophecy about the Antichrist, rampant war, world conquest, and the like, but the Second Coming did not occur.
We must go back much farther than American fundamentalism to understand "old" Christianity. "Old-time religion" is only old in the way that Def Leppard is an "ancient band." One can use the term as a descriptor and people will know what is meant, but it certainly is not literally true. There are nearly 1900 years of Christianity before "old-time religion."
(1) Joel Carpenter, Revive Us Again: the Reawakening of American Fundamentalism, (New York: Oxford University Press, 1997), 31-34, 138-140.