EB2 Priority date

Is EB2 priority date base on the date that DOL recevied the LCA application? the post stamp date?

Wikipedia says 

For employment-based immigration beneficiaries, the priority date is the date an immigration petition is filed at USCIS, under categories where a labor certification is not required, or when United States Department of Labor receives a labor certification application, under categories where a labor certification is required. In all cases, the priority dates are not established until USCIS approves the immigration petition.