Keeping? What do you mean?
The Christians are not required to keep the feasts. The first council of Jerusalem recorded in Acts 15 tells us we are not required to keep the law of Moses. Paul tells us in his writings in a continuous theme that the ceremonial laws pointed to Christ and His ministry.
The central element in every OT feast was the sacrifice. That has been fulfilled by Christ's sacrifice. More specifically for SDA's, we are the 7th month movement, the month of Tishri. Tishri 10th, the day of atonement has began to be fulfilled by Christ when He began His ministry in the Most Holy place in the heavenly sanctuary in 1844.