ACA Full-Time Flag - Date Tracked?

I've heard three different answers to when the ACA Full-Time Flag needs to be checked.

1. Originally I was informed that the full time flag was to be check when the employee's benefits would be effective, regardless of if the employee took the benefit offer or not. Example: We have a waiting period of the first of the month following 30 days of hire. FT EE hired 11/19/2015 would have the full time flag checked on 01/01/2016.
2. I was then informed, and based on what I understand from the last webcast, that the full time flag needs to be check when the person is benefit eligible. Using the same example as above, the FT EE would have the flag checked as of 11/19/2015. If your health plans are configured with the waiting period built it, the reporting will take that into account to produce the required 2D code for the months the employee is not enrolled. Otherwise, you'd use the SIT and Assessment Period to indicate the waiting period.