Lambert (P) filed a class action in federal court against Nutraceutical (D) alleging that D's dietary supplement ran afoul of California consumer-protection law. On February 20, 2015, the District Court revisited the class certification decision and ordered the class decertified. Under Rule 23(f) P had 14 days to ask the Court of Appeals for the Ninth Circuit for permission to appeal the order. Instead of filing a petition for permission to appeal, P informed the District Court on March 2 (10 days after the decertification order) that he would “want to file a motion for reconsideration” in the near future. The court told P to file any such motion “no later than” March 12. Neither P nor the District Court mentioned the possibility of an appeal. P filed his motion for reconsideration 20 days after the decertification order. The District Court denied the motion on June 24, 2015. Fourteen days later, on July 8, P petitioned the Court of Appeals for permission to appeal the decertification order. D argues that this was untimely because more than four months had elapsed since the District Court’s February 20 order decertifying the class, far more than the 14 days that Federal Rule of Civil Procedure 23(f) allows. The Court of Appeals held that the Rule 23(f) deadline should be “tolled” under the circumstances. It reasoned that Rule 23(f)’s time limit is “non-jurisdictional and that equitable remedies softening the deadline are therefore generally available.” Tolling was warranted, because P “informed the court orally of his intention to seek reconsideration” within Rule 23(f)’s 14-day window, complied with the March 12 deadline, and “otherwise acted diligently.” The Court of Appeals held that the District Court abused its discretion in decertifying the class. It reversed the decertification order. D appealed.