The AMA site has updated information about the FAA UAS registration process posted.
The AMA FAQ Blog says that the free registration cutoff date is February 19th, and the
actual date posted on the FAA site https://www.faa.gov/uas/registration/ is
“Register before midnight EST, January 20th, 2016 and your $5 registration fee will be refunded!”
So if you wish to take advantage of the free registration period do so before January 20th.
This is just just an update email from recent changes noted on the AMA web site.