Two of those demonstrations are uncrewed flight tests, known as Orbital Flight Test for Boeing, and Demonstration Mission 1 for SpaceX. After the uncrewed flight tests, both companies will execute a flight test with crew prior to being certified by NASA for crew rotation mission.
The following schedule reflects the most recent publicly-releasable dates for both providers.
Targeted Test Flight Dates:
SpaceX Demonstration Mission 1: February 2018
SpaceX Demonstration Mission 2 (crewed): June 2018
Boeing Orbital Flight Test: June 2018
Boeing Crew Flight Test: August 2018