Millions of Mormons will participate in a global general conference today and tomorrow that will make church history.

They will sustain new President Russell M. Nelson as the 17th leader of The Church of Jesus Christ of Latter-day Saints in a solemn assembly.

He is expected to call two new apostles to fill vacancies created by the deaths of his predecessor, President Thomas S. Monson, in January and Elder Robert D. Hales during the last general conference in October.

Today will be the first time President Nelson will speak to the entire church since he was introduced as the faith’s new leader in a broadcast on Jan. 15, when he pledged to serve God and church members “with every remaining breath of my life.”

Today also marks the first time a church president has spoken at a semiannual conference since April 2017. President Monson was unable to attend the October conference because of poor health.

President Nelson is expected to speak multiple times during the conference, which includes three sessions today at 10 a.m., 2 p.m. and 6 p.m. MDT at the 21,000-seat Conference Center across from Temple Square in downtown Salt Lake City.

Sunday sessions are at 10 a.m. and 2 p.m. MDT.