SDA started when a 19th-Century sect called the Adventists fell apart after a prediction of the end of the world failed to come to pass. Ellen Gould White said that she was receiving messages from three angels explaining where the Adventists had gone wrong.
She pointed to Sunday church services as the main problem in Christianity of her time and advocated other changes as well. She had books published with unsupported histories of Christianity declaring the Catholic Church to be a conspiracy to draw people away from real, seventh-day, worship by getting them to worship on Sunday. She also said the wine the New Testament talks about was grape juice, a “health-giving beverage.” In reality, wine is neither more nor less health-giving than grape juice, but this was part of SDA lifestyle theory. They also hold a vegan diet nutritionally and spiritually superior.
They have foot-washing every Saturday.
They expect a persecution for their Saturday worship. It’s very central to their worldview.
I was once interested in the SDA because of the vegetarian-health-food idea, but quickly found the doctrine unpersuasive.
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