The word advent simply means “coming.” Many Christians observe and celebrate Advent in preparation for Christmas, as they remember Christ’s coming to earth as a baby. The future return of Christ is often called the second coming or the second advent. Broadly speaking, anyone who expects Christ to return might be referred to as an Adventist. However, the term Adventist is normally reserved for people or groups who expect Christ to return at any moment, or who at least allow for that possibility. Postmillennialists and those who believe in a post-tribulation rapture would not fall into this category; however, those who believe in a pre-tribulation rapture would. (In this sense, even Got Questions could be considered an Adventist group.) Even though the rapture is not synonymous with the second advent, it is seen as the “opening act” of the second advent. Beyond the broad theological meaning that could apply to a great number of Christians, a limited number of groups through the years have been referred to as Adventists.
The beginning of Adventism as a movement is often credited to William Miller, a preacher who predicted that Jesus Christ would return some time in 1843 or 1844. Trusting Miller, his followers withdrew from society and waited. This resulted in what is referred to as the Great Disappointment of 1844. When Jesus did not return when Miller predicted He would, most of the Millerites went back to their normal lives. Miller continued to express confidence in the return of Christ but admitted that he may have made some errors in his calculations.
Today, there are two major groups that have the label “Advent” or “Adventist” in their names.
Seventh-day Adventists arose directly from the theological line of William Miller through the further teachings of Ellen G. White. There are many doctrinal problems with Seventh-day Adventism, but the name “Seventh-day Adventists” refers to two parts of their theology: they observe the seventh day (Saturday) as a Sabbath, and they expect the Lord to return at any time. They are Adventists who observe the seventh day.
The Advent Christian Church is another significant body with “advent” in its name. Sometimes they refer to themselves as “First-day Adventists.” There are some significant differences between Advent Christians and Seventh-day Adventists, although both trace their development back to William Miller. Advent Christians are generally orthodox with the exception that they teach “soul sleep,” which means that, when a person dies, he “sleeps” until the return of Christ—in other words, the soul is not consciously aware of anything until it is reunited with the resurrected body at the second advent or, in the case of unbelievers, resurrected for judgment. This doctrine is an error as the Scriptures teach that, for the believer, to be absent from the body is to be present with the Lord (Philippians 1:23).
Another problem with the Advent Christian Church is clarity regarding the means of salvation. Neither their Statement of Faith nor the Declaration of Principles (an elaboration on their statement of faith) contains an unambiguous statement of “justification by faith alone,” so it is not uncommon to find some within the Advent Christian Church who are trusting Christ alone for salvation and others who are holding on to some mixture of faith and works. (The same can be said of many churches that do have clear statement regarding justification by faith!)
In addition to these two major groups, there are a number of minor Adventist groups.
In the final analysis, all Adventists hold in common an expectation of the imminent return of Christ. Beyond that belief, there are a great many differences that have to be examined and evaluated separately. While Scripture does teach us to expect the return of Christ at any time, setting dates and making specific predictions is always unbiblical (see Matthew 24:36).