Cut-off Date: 

The date determines whether a preference immigrant visa applicant can be scheduled for an immigrant visa interview in any given month.  The cut-off date is the priority date of the first applicant who could not get a visa interview for a given month.  Applicants with a priority date before or earlier than the cut-off date can be scheduled.  However, if your priority date is later (comes after) the cut-off date, you will need to wait longer, until your priority date is reached (becomes current).