https://www.uscis.gov/visabulletininfo

If USCIS determines that there are more immigrant visas available for a fiscal year than there are known applicants for such visas, we will state on this page that you may use the Dates for Filing Visa Applications chart. Otherwise, we will indicate on this page that you must use the Application Final Action Dates chart to determine when you may file your adjustment of status application.

For Employment-Based Filings:
You must use the Application Final Action Dates chart in the Department of State Visa Bulletin for March 2016.