29 U.S.C. § 257: Pending collective and representative actions

The statute of limitations prescribed in section 255(b) of this title shall also be applicable (in the case of a collective or representative action commenced prior to May 14, 1947 under the Fair Labor Standards Act of 1938, as amended [ 29 U.S.C. 201 et seq.]) to an individual claimant who has not been specifically named as a party plaintiff to the action prior to the expiration of one hundred and twenty days after May 14, 1947 . In the application of such statute of limitations such action shall be considered to have been commenced as to him when, and only when, his written consent to become a party plaintiff to the action is filed in the court in which the action was brought.