How is the I-485 filing priority date determined?

The dates for filing of the adjustment of status application assume that the I-526 has been approved. There is no concurrent AOS filing allowed for I-526. The USCIS makes a separate announcement monthly regarding whether the dates for filing or the final action dates may be used. In October and November of last year, USCIS accepted I-485s and allowed the dates for filing to be used. Since then, it has not and only the final action dates may be used.

The Department of State determines these dates based on past and projected volume of cases. It seems that there is a split between Adjustment of Status (I-485) and U.S. consulate/NVC cases. We would need to look at your specific situation to make a fully informed decision on how to move forward.

USCIS every month publishes whether they will use Date for Filing, or Final Action Date for filing adjustments. For October and November we could use DFF; so far this year, only FAD.

When the I-526 is approved it will show the priority date (this is the date that the I-526 was filed originally.)

A few months ago, President Obama issued an order to allow the EB-5 applicants whose I-526s have been approved to wait in the United States. So, there are two priority dates for the EB-5 applicants. Actually, this order is not valid, so the EB-5 applicants still need to wait for the priority date on the I-526 receipts.

I am not well-versed in the State Department visa numbers, and the Mainland China category is very confusing. Many practitioners will only answer questions on a "case by case" basis because of the complexities. I believe that the 01/15/14 date refers to applications with a date prior to that and that if you have one you may now apply for a visa with the NVC, I do not believe it refers to the I-485. As I said, it is often on a case by case basis so you may wish to consult immigration counsel.