...far surpassing 2017’s enrollment Nationwide, open enrollment for 2018 coverage began November 1, 2017, and in most states, it ended on December 15, 2017. But state-run exchanges had some flexibility with the dates, as HHS revised the scheduled open enrollment period in April 2017. (It had previously been slated to last three months), and acknowledged that state-run exchanges might not be able to make the changes necessary to switch to the new schedule by the fall of 2017.