Publication process in a journal I have a paper with revise and resubmit in a journal of Elsevier. In one part of the mail, the editor wrote me this:


  If you choose to revise your manuscript it will be due into the
  Editorial Office by the Aug 30, 2018.
  
  The deadline is given only because we want you to give a high priority
  to revision of this submission. We assure you that a revision will be
  reviewed normally even if it is submitted after the deadline.


I do not understand this deadline. If the paper is reviewed normally even if it is submitted after the deadline, why do they put a deadline?

So is it possible to submit the revised version after the deadline?
Journals have deadlines for publication. Everything that will go into issue X needs to be ready by date Y. If you meet their deadlines you increase your chances for early publication, otherwise you may be put off. 

However another problem is that while the reviewing is "normal" the editorial process of choosing papers for issue X also comes in to play. The other language of the publisher's reply might imply conditional acceptance if returned by the date given. After that, unless you already have acceptance, it might become more tenuous. 

Basically, what they are saying is "We have constraints here. Please help us meet them." It would be good, if not essential, to honor that.