Alex Deucher of the X.Org Foundation's election committee has sent out the list of important dates in an email to X.Org Foundation members:
19 Feb 2017 Nomination period begins
05 Mar 2017 Nomination period ends
05 Mar 2017 Publish slate of candidates
05 Mar 2017 Deadline for new membership applications and renewals
05 Mar 2017 Nominee Q&A period begins
12 Mar 2017 Nominee Q&A period ends
12 Mar 2017 Election period begins
26 Mar 2017 Election period ends
27 Mar 2017 Election committee presents results to the current X.Org board for certification
27 Mar 2017 Results published to the membership
This year's elections are not only for the four board seats with terms expiring this year, but there is also a vote to change the membership agreements. The changes to the membership agreement are documented in Git. Basically there is some long overdue updates like removing references to X.Org at trade show booths (it hasn't done that in many years), there is no X.Org Architecture Group, X.Org now uses Git rather than CVS, etc.
The board members with terms expiring this year include Rob Clark, Martin Peres, Peter Hutterer, and Daniel Vetter. Details on the current board make-up via this Wiki page.
Those that have contributed to X.Org/Mesa/Wayland in some manner need to renew their membership by 5 March. Doing so or applying for the first time can be done via members.x.org.