; or (ii) the date that is 90 days after the date of the enactment of the E–Verify System Act of 2018. (B) Federal contractors Federal contractors shall participate in the System as provided in the final rule relating to employment eligibility verification published in the Federal Register on November 14, 2008 (73 Fed. Reg. 67,651), or any similar subsequent regulation, for which purpose references to E–Verify in the final rule shall be construed to apply to the System. (C) Critical infrastructure (i) In general Beginning on the date that is 1 year after the date on which regulations are published implementing this subsection, the Secretary may authorize or direct any employer, person, or entity responsible for granting access to, protecting, securing, operating, administering, or regulating part of the critical infrastructure (as defined in section 1016(e) of the Critical Infrastructure Protection Act of 2001 ( 42 U.S.C. 5195c(e) )) to participate in the System to the extent the Secretary determines that such participation will assist in the protection of the critical infrastructure. (ii) Notification to employers The Secretary shall notify an employer required to participate in the System under this subparagraph not later than 90 days before the date on which the employer is required to participate. (D) Employers with more than 5,000 employees Not later than 2 years after regulations are published implementing this subsection, all employers with more than 5,000 employees shall participate in the System with respect to all newly hired employees and employees with expiring temporary employment authorization documents. (E) Employers with more than 500 employees Not later than 3 years after regulations are published implementing this subsection, all employers with more than 500 employees shall participate in the System with respect to all newly hired employees and employees with expiring temporary employment authorization documents. (F) Agricultural employment Not later than 4 years after regulations are published