USCIS has announced that for December, Family-Based Adjustment of Status applicants can use the "Filing Dates" listed on the Department of State's December 2015 Visa Bulletin. Employment-Based Applicants, however, can only use the "Final Action Dates" to determine when they are eligible to submit Adjustment of Status applications.
This announcement comes after USCIS issued updated instructions regarding the use of the Revised Visa Bulletin, implemented in September 2015, which contains two sets of dates for both family-based and employment-based immigrant visas.