William Miller, an American pastor, predicted that Christ would return to earth on October 22, 1844. His followers gathered in their churches on that day to worship and wait.
They experienced the Great Disappointment, as it was later called, and Miller disconnected from the movement he started. But the faithful followers claimed they received later revelations, notably from Ellen White.
Like many people in the mid-1850s, she was diet- and health-conscious (does any of this sound familiar?). She urged Miller’s former followers to follow the Old Testament dietary laws and to keep the Sabbath as God intended—on Saturday, that is.
The Seventh-day Adventists today use the Bible as their guide and are most noted (as their name indicates) for worshipping on Saturday.
Most still follow the kosher laws in Leviticus 11, and some are strict vegetarians (a practice the Bible says nothing about, by the way).