Take a look at the schedule:
First day: April 16
Phase I: April 16-29
Phase II: April 30-May 20
Phase III: May 21-June 17
OTAs: May 21-22, May 24, May 29-31, June 4-7
Rookie minicamp: May 11-12
Mandatory minicamp: June 12-14
As per the NFL’s Collective Bargaining Agreement:
Phase One consists of the first two weeks of the program with activities limited to strength and conditioning and physical rehabilitation only.
Phase Two consists of the next three weeks of the program. On-field workouts may include individual player instruction and drills as well as team practice conducted on a "separates" basis. No live contact or team offense vs. team defense drills are permitted.
Phase Three consists of the next four weeks of the program. Teams may conduct a total of 10 days of organized team practice activity, or "OTAs". No live contact is permitted, but 7-on-7, 9-on-7, and 11-on-11 drills are permitted.
Article 22 of the Collective Bargaining Agreement stipulates that clubs may hold one mandatory minicamp for veteran players. This minicamp...must occur during Phase Three of the offseason program.
Each club may hold a rookie football development program for a period of seven weeks, which in 2017 may begin on May 15. During this period, no activities may be held on weekends, with the exception of one post-NFL Draft rookie minicamp, which may be conducted on either the first or second weekend following the draft.
(UPDATED May 2)
The NFL has released the confirmed dates of rookie minicamps. The Rams will hold theirs next week. As Rams Head Coach Sean McVay put it in the post-draft press conference though, it won’t be a traditional rookie minicamp:
We’ll have something more similar to a tryout camp. That will be in a couple weeks. You look at some of the people that we envision adding to really get us to around that 87 to 88, and then you’ve got a couple spots to get up to your 90 (man roster) allotment. I think we’ll use that as an opportunity to see if we can find some spots just based on the numbers and how we want to allocate that 90 over the course of some of the different positions.