Pete Greig is an author, pastor, and the founding champion of 24-7 Prayer, an international, interdenominational movement of prayer, mission, and justice. Pete also leads Emmaus Road Church and serves as director of Prayer for Holy Trinity Brompton--one of the most influential churches in Europe--and Alpha International in London. Pete lives with his wife, Sammy, and their two children in Guildford, Surrey, UK. Dave Roberts is a pastor, speaker, and author or coauthor of several books, including the bestseller The Grace Outpouring with Roy Godwin.
The title comes from a verse in Joel from the Holy Bible: "The sun will be turned to darkenss and the moon to blood before the great and glorious day of the Lord. And everyone who calls on the name of the Lord will be saved."