Starting in September 2017, some ACT test-takers with a specific category of special accommodations (“Timing Code 6,” which means 50% extra time) will have a slightly modified testing schedule.
What is changing
When a student who has been given “time and a half” accommodations on the ACT (meaning 50% extra time to take the test) takes the ACT, the student will have five self-paced hours to complete the four test sections (English, Mathematics, Reading, and Science). When that five hours is up, the test-taker will have an enforced break and then will have one hour to complete the ACT essay.
(In the past, test-takers had six hours to complete all sections at her own pace.)
Note that if you’re planning not to take the writing section of the ACT, this does not apply to you–you will still have five self-paced hours for your ACT.
Then vs. now
Before the change: 6 hours for all sections
After the change: 5 hours for test sections + 1 hour for the essay
Why is ACT making the change?
ACT says that they’re making the change to make it “fair” and to give the “same amount of time” for the multiple-choice test sections (i.e., everyone will have five hours to work on the test sections).
But reading between the lines a bit (so to speak), it would seem that in some cases, test-takers who had six hours for the entire test (including the writing section) may have sacrificed some of writing time to work longer on the test sections. For example, it’s theoretically possible that some test-takers would spend six hours on the four test sections and no time on the writing. For these people, again hypothetically, this could cause their reported score to be higher than people who did not sacrifice essay-writing time.
Remeber: For many people and admissions departments, the reported ACT score (for example, 32) is much more important than the writing score. This fact gives people an incentive to score as high as possible on the multiple-choice sections, even if doing so means getting a lower score on the ACT writing.
From the horse's mouth: http://www.act.org/content/dam/act/secured/documents/ExtendedTimePolicy-FAQ.pdf