Subsequent to the issuance of the December 2017 Visa Bulletin, USCIS has informed prospective applicants of which priority-date chart should be referenced for applications submitted/processed in December:

Family-Based Applicants: Dates for Filing chart

Employment-Based Applicants: Final Action Dates chart

The relevant charts can be seen below.

Family-Based Applicants

Next month, family-based applicants should consult the Dates for Filing chart for December (see below).

Employment-Based Applicants

Employment-based applicants should consult the Final Action chart for December (see below).