The retrocession is effective within the time frame specified in the funding agreement. In the absence of a specified date, the retrocession becomes effective:

(a) On the earlier of 1 year after the date of the Tribe's submission of the request, or the date on which the funding agreement expires; or

(b) Such date mutually agreed upon by the Departments and the retroceding Tribe when the Department of the Interior has agreed to assume a retroceded PSFA.