delivered the opinion of the Court.
The initial question in this case is one of jurisdiction— whether the petition for certiorari was filed within the period allowed by law.1 We hold that it was not.
The cause grows out of a proceeding initiated by petitioner, the Federal Trade Commission, in 1943. At that time, the Commission issued a three-count complaint against respondent. Count I charged a violation of § 5 of the Federal Trade Commission Act;2 Count II charged a violation of § 3 of the Clayton Act;3 Count III dealt with an alleged violation of § 2 (a) of the Clayton Act as amended by the Robinson-Patman Act.4 A protracted administrative proceeding followed. The Commission finally determined against respondent on all three counts, *208and it issued a cease and desist order, in three parts, covering each of the three violations.
Respondent petitioned the Court of Appeals for the Seventh Circuit to review and set aside this order. The Commission sought enforcement of all parts of its order in a cross-petition.
Respondent abandoned completely its attack on Parts I and II of the order. In briefs and in oral argument, respondent made it clear that the legality of Part III was the only contested issue before the Court of Appeals. Neither party briefed or argued any question arising out of Parts I and II.
On July 5, 1951, the Court of Appeals announced its decision. The opinion stated that since respondent did not “challenge Parts I and II of the order based on the first two counts of the complaint we shall make no further reference to them.” The court then went .on to hold that Part III of petitioner’s order could not be sustained by substantial evidence and should be reversed. 191 F. 2d 786. On the same day, the court entered its judgment, the pertinent portion reading as follows:
“. . . it is ordered and adjudged by this Court that Part III of the decision of the Federal Trade Commission entered in this cause on January 14, 1948, be, and the same is hereby, Reversed, and Count III of the complaint upon which it is based be, and the same is hereby Dismissed.”
The Court of Appeals requires petitions for rehearing to be filed “within 15 days after entry of judgment.” The Commission filed no such petition. On August 21, 1951, long after the expiration of this 15-day period, and after a certified copy of said judgment, in lieu of mandate, was issued, the Commission filed a memorandum with the court which reads in part as follows:
*209“On July 5, 1951 the Court entered its opinion and judgment reversing Part III of the decision of the Federal Trade Commission dated January 14, 1948 and dismissing Count III of the complaint upon which it is based. No disposition has been made of the Cross-Petition filed by the Commission for affirmance and enforcement of the entire decision. The Commission takes the position that its Cross-Petition should be in part sustained, i. e., to the extent that the Court should make and enter herein a decree affirming Parts I and II of the Commission’s order to cease and desist and commanding Minneapolis-Honeywell Regulator Company to obey the same and comply therewith. . . .
“11. In its briefs filed herein the petitioner abandoned its attack upon Parts I and II of the order and challenged only the validity of Part III of the order (see page 1 of petitioner’s brief dated March 15, 1951). Thus, petitioner concedes the validity of Parts I and II of the order and does not contest the prayer of the Commission’s Cross-Petition and brief with respect to the affirmance and enforcement of Parts I and II of the order.”
Clearly, by this memorandum the Commission sought no alteration of the judgment relative to Part III; in fact, it acknowledged the entry of judgment reversing Part III on July 5, 1951. It did not even claim it to be a petition for rehearing. It was submitted that Parts I and II of the order were uncontested, and “In conclusion . . . submitted that the Court should make and enter ... a decree affirming and enforcing Parts I and II of the Commission’s order to cease and desist.”
On September 18, 1951, the Court of Appeals issued what it called its “Final Decree.” Again the court *210“ordered, adjudged and decreed” that Part III of the Commission’s order “is hereby reversed and Count III of the complaint upon which it is based be and the same is hereby dismissed.” The court then went on to affirm Parts I and II, and it entered a judgment providing for their enforcement, after reciting again that there was no contest over this phase of the order.
On December 14, 1951, the Commission filed its petition for certiorari. Obviously, the petition was out of time unless the ninety-day filing period began to run anew from the second judgment entered on September 18, 1951. In our order granting certiorari, 342 U. S. 940, we asked counsel to discuss the “timeliness of the application for the writ.”
Petitioner refers us to cases which have held that when a court considers on its merits an untimely petition for. a rehearing, or an untimely motion to amend matters of substance in a judgment, the time for appeal may begin to run anew from the date on which the court disposed of the untimely application.5
Petitioner apparently would equate its memorandum of August 21, 1951, with an untimely petition for a rehearing affecting Part III. But certainly its language and every inference therein is to the contrary. When petitioner filed its memorandum, the time for seeking a rehearing had long since expired.
Moreover, the memorandum was labeled neither as a petition for a rehearing nor as a motion to amend the previous judgment, and in no manner did it purport to seek such relief. On the contrary, the Commission indicated that it was quite content to let the Court of Appeals’ decision of July 5 stand undisturbed. Since we cannot *211treat the memorandum of August 21 as petitioner would have us treat it, we cannot hold that the time for filing a petition for certiorari was enlarged simply because this paper may have prompted the court below to take some further action which had no effect on the merits of the decision that we are now asked to review in the petition for certiorari.
Petitioner tells us that the application must be deemed to be in time because “when a court actually changes its judgment, the time to appeal or petition begins to run anew irrespective of whether a petition for rehearing has been filed.” 6 We think petitioner’s interpretation of our decisions is too liberal.
While it may be true that the Court of Appeals had the power to supersede the judgment of July 5 with a new one,7, it is also true, as that court itself has recognized, that the time within which a losing party must seek review cannot be enlarged just because the lower court in its discretion thinks it should be enlarged.8 Thus, the mere fact that a judgment previously entered has been reentered or revised in an immaterial way does not toll the time within which review must be sought.9 Only when the lower court changes matters of substance,10 or resolves a genuine ambiguity,11 in a judgment previously rendered should the period within which an appeal must be taken or a petition for certiorari filed begin to run *212anew. The test is a practical one. The question is whether the lower court, in its second order, has disturbed or revised legal rights and obligations which, by its prior judgment, had been plainly and properly settled with finality.12
The judgment of September 18, which petitioner now seeks to have us review, does not meet this test. It reiterated, without change, everything which had been decided on July 5. Since the one controversy between the parties related only to the matters which had been adjudicated on July 5, we cannot ascribe any significance, as far as timeliness is concerned, to the later judgment.13
Petitioner puts great emphasis on the fact that the judgment of September 18 was labeled a “Final Decree” by the Court of Appeals, whereas the word “Final” was missing from the judgment entered on July 5. But we think the question of whether the time for petitioning for certiorari was to be enlarged cannot turn on the adjective which the court below chose to use in the caption of its second judgment. Indeed, the judgment of July 5 *213was for all purposes final. It put to rest the questions which the parties had litigated in the Court of Appeals. It was neither “tentative, informal nor incomplete.” 14 Consequently, we cannot accept the Commission's view that a decision against it on the time question will constitute an invitation to other litigants to seek piecemeal review in this Court in the future.
Thus, while we do not mean to encourage applications for piecemeal review by today’s decision, we do mean to encourage applicants to this Court to take heed of another principle — the principle that litigation must at some definite point be brought to an' end.15 It is a principle reflected in the statutes which limit our appellate jurisdiction to those cases where review is sought within a prescribed period. Those statutes are not to be applied so as to permit a tolling of their time limitations because some event occurred in the lower court after judgment was rendered which is of no import to the matters to be dealt with on review.
Accordingly, the writ of certiorari is
Dismissed.
28 U. S. C. §2101 (e).
38 Stat. 719, 15 U. S. C. § 45.
38 Stat. 731, 15 ü. S. C. §14.
38 Stat. 730, as amended, 49 Stat. 1526, 15 U. S. C. § 13 (a).
Pfister v. Finance Corp., 317 U. S. 144, 149 (1942); Bowman v. Loperena, 311 U. S. 262, 266 (1940); Wayne United Gas Co. v. Owens-Illinois Co., 300 U. S. 131, 137-138 (1937).
Brief for petitioner, p. 43.
28 U. S. C. §452; see Zimmern v. United States, 298 U. S. 167 (1936).
See Fine v. Paramount Pictures, 181 F. 2d 300, 304 (1950).
Department of Banking v. Pink, 317 U. S. 264 (1942); Toledo Scale Co. v. Computing Scale Co., 261 U. S. 399 (1923); Credit Co., Ltd. v. Arkansas Central R. Co., 128 U. S. 258 (1888).
See Zimmern v. United States, 298 U. S. 167, 169 (1936); compare Department of Banking v. Pink, supra.
Compare Federal Power Commission v. Idaho Power Co., 344 U. S. 17 (1952).
Compare Rubber Co. v. Goodyear, 6 Wall. 153 (1868) (appeal allowed from a second decree, restating most provisions of the first because the first decree, at the time of entry, was only regarded by the parties and the court as tentative); Memphis v. Brown, 94 U. S. 715 (1877) (appeal allowed from second judgment on the ground that the second made material changes in the first). See United States v. Hark, 320 U. S. 531, 533-534 (1944); Hill v. Hawes, 320 U. S. 520, 523 (1944).
The suggestion is made that the September 18 judgment injected a new controversy into the litigation — the question of whether the Court of Appeals had the power to affirm and enforce the Commission’s order after it had cross-petitioned for such relief. Cf. Federal Trade Commission v. Ruberoid Co., 343 U. S. 470 (1952). But if the respondent had sought to contest that issue, it could have done so from the start, by raising objections to enforcement of all parts of the Commission’s cross-petition. Instead, respondent refused to contest these'parts of the Commission’s order. Having done so, it removed the question involved in the Ruberoid case from this case.
See Dickinson v. Petroleum Conversion Corp., 338 U. S. 507, 514 (1950).
See Matton Steamboat Co. v. Murphy, 319 U. S. 412, 415 (1943).