Introducing change to users

Lately I started monetizing my website and I had to introduce changes to the website users. I have over 600 users, and I am still not sure whether I did the right thing by assigning a definite date for implementing the change. I have communicated the change for two months before implementation, but I have set a definite date for implementation and moved forward with it.



In your opinion is it more effective to introduce change gradually? or is it better to set a definite date to implement the change and put up with all the complaints?