ACA Full Time Flag - Date to Use?

Our benefit eligible employees have a waiting period of first of the month following 30 days of hire.

For employees hired on 01/01/15 or later does the ACA Full Time Check box need to be checked as of the employee's hire date or when the employee is actually eligible to receive the benefit.

Example: Employee hired 02/15/15.

Does the ACA Full Time Check Box get checked as of 02/15/15 or 04/01/15 (first of the month following 30 days from hire)?