February 20 First day for clubs to designate Franchise or Transition Players.
March 6 Prior to 4:00 p.m., deadline for clubs to designate Franchise or Transition Players.
March 14 The 2018 league year and free agency period begin at 4:00 p.m.
April 26-28 2018 NFL Draft, AT&T Stadium, Arlington, TX.
https://operations.nfl.com/football-ops/league-governance/2018-important-nfl-dates/