J. SKELLY WRIGHT, Circuit Judge:
Debora Gordon appeals from an order dismissing her suit against her former employer, the National Youth Work Alliance (NYWA), charging it with violations of Title VII of the Civil Rights Act of 1964, 42 U.S.C. § 2000e et seq. (1976 & Supp. Ill 1979), and with violations of 42 U.S.C. §§ 1981, 1985 (1976) and the District of Columbia’s Human Rights Law, 1 D.C.Code § 2550 et seq. (1981). The District Court granted appellee NYWA’s motion to dismiss solely on the basis that the court lacked subject matter jurisdiction because the plaintiff had not filed suit within the 90-day time limit prescribed by Title VII, see 42 U.S.C. § 2000e-5(f)(l) (1976). We reverse.1
NYWA fired appellant, a black woman, in December 1979, shortly after she had a series of disputes with her white, male supervisors. She filed charges of discrimination with the Equal Employment Opportunity Commission (EEOC) and the District of Columbia Office of Human Rights, neither of which found reasonable cause to pursue her complaint. The EEOC regional office in Baltimore accordingly sent Gordon a notice of her right to sue, dated with a stamp in the lower left corner “OCT 07 1980.” The notice letter was mailed to Gordon’s home address in Washington, D.C., return receipt requested, and the Postal Service eventually returned the following receipt to the Baltimore EEOC office:
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J. SKELLY WRIGHT, Circuit Judge:
Debora Gordon appeals from an order dismissing her suit against her former employer, the National Youth Work Alliance (NYWA), charging it with violations of Title VII of the Civil Rights Act of 1964, 42 U.S.C. § 2000e et seq. (1976 & Supp. Ill 1979), and with violations of 42 U.S.C. §§ 1981, 1985 (1976) and the District of Columbia’s Human Rights Law, 1 D.C.Code § 2550 et seq. (1981). The District Court granted appellee NYWA’s motion to dismiss solely on the basis that the court lacked subject matter jurisdiction because the plaintiff had not filed suit within the 90-day time limit prescribed by Title VII, see 42 U.S.C. § 2000e-5(f)(l) (1976). We reverse.1
NYWA fired appellant, a black woman, in December 1979, shortly after she had a series of disputes with her white, male supervisors. She filed charges of discrimination with the Equal Employment Opportunity Commission (EEOC) and the District of Columbia Office of Human Rights, neither of which found reasonable cause to pursue her complaint. The EEOC regional office in Baltimore accordingly sent Gordon a notice of her right to sue, dated with a stamp in the lower left corner “OCT 07 1980.” The notice letter was mailed to Gordon’s home address in Washington, D.C., return receipt requested, and the Postal Service eventually returned the following receipt to the Baltimore EEOC office:
[359]*359
It is signed by one Vinona Gordon, apparently appellant’s mother, and dated, apparently in the same hand, “10-7-80.” There is also a round stamp in the space marked “Postmark” showing the date as “OCT 9 1980.” Appellant filed suit in the District Court on January 7, 1981 — 90 days after October 9, but 92 days after October 7.
NYWA submitted a motion to dismiss for lack of subject matter jurisdiction, citing Federal Rule of Civil Procedure 12(b)(1) and attaching copies of the right-to-sue letter and the return receipt. The gravamen of NYWA’s motion was that Gordon received notice of her right to sue on October 7, the handwritten date on the return receipt. Gordon opposed the motion on the ground that it was more likely that the letter was sent on October 7 and received on October 9, given the dates stamped on the letter and the receipt. The District Court granted NYWA’s motion in a brief order:
Upon consideration of defendant’s motion to dismiss for lack of jurisdiction over the subject matter, the opposition thereto, and the entire record herein, and it appearing to the Court that the plaintiff has failed to timely file her complaint pursuant to 42 U.S.C. § 2000e-5(f)(l) (1976) plaintiff’s action must be dismissed for lack of subject matter jurisdiction. McDonnell Douglas Corporation v. Green, 411 U.S. 792, 798 [93 S.Ct. 1817, 1822, 36 L.Ed.2d 668] (1973); Wong v. Bon Marche, 508 F.2d 1249 (9th Cir. 1975). * *
Appendix A to appellant’s brief at A-l.
Title VII requires that plaintiffs file suit within 90 days of receiving notice from the EEOC of their right to sue. 42 U.S.C. § 2000e-5(f)(l) (1976). The sole question at issue in this case is how a defendant and the court should treat a motion to dismiss based on the defendant’s contention that the plaintiff has filed suit after expiration of the 90-day period. NYWA moved to dismiss on this basis under Rule 12(bXl), and it supported its theory that Rule 12(b)(1) applied with the argument that “[f]ailure to bring an action under the section within 90 days deprives a federal court of subject, matter jurisdiction.” Motion to Dismiss for Lack of Jurisdiction Over the Subject Matter at 2, reproduced in Appendix A to appellant’s brief at A-13, citing Hinton v. CPC International, Inc., 520 F.2d 1312, 1315 (8th Cir. 1975). The sentence quoted from Hinton, however, is not apposite to this case. It refers to a long-standing dispute among the circuits as to what the Supreme Court meant by referring to the time limits for bringing suit under Title VII as “jurisdictional,” see Alexander v. Gardner-Denver Co., 415 U.S. 36, 47, 94 S.Ct. 1011, 1019, 39 L.Ed.2d 147 (1975); McDonnell Douglas Corp. v. Green, 411 U.S. 792, 798, 93 S.Ct. 1817, 1822, 36 L.Ed.2d 668 (1973),2 The Supreme Court has now sub[360]*360stantially resolved this dispute in Zipes v. Trans World Airlines, Inc.,-U.S.-, 102 S.Ct. 1127, 71 L.Ed.2d 234 (1982), which holds that “filing a timely charge of discrimination with the EEOC is not a jurisdictional prerequisite to suit in a federal court, but a requirement that, like a statute of limitations, is subject to waiver, estoppel, and equitable tolling.” Id. at -, 102 S.Ct. at 1132.
Statutes of limitations generally create affirmative defenses. Although affirmative defenses may be raised on a motion to dismiss, the proper method for raising a defense of limitation is a motion under Rule 12(b)(6), not a motion under Rule 12(b)(1). • See 5 C. Wright & A. Miller, Federal Practice and Procedure § 1277 at 331-332 (1969 ed.). The difference between them is that under Rule 12(b)(6) the court may not consider matters outside the pleadings and accompanying legal memoranda without converting the motion into one for summary judgment and affording all parties “reasonable opportunity to present all material made pertinent to such a motion by Rule 56.” Fed.R.Civ.P. 12(b). The purpose of this proviso, added in the 1946 Amendments to the Federal Rules, was twofold: it gave the District Courts authority to consider factual material at the motion to dismiss stage, but it also sought “to avoid taking a party by surprise * * See Notes of Advisory Committee on 1946 Amendment to Rules, 28 U.S.C. app. at 409-410 (1976).
Precisely because of this safeguard in Rule 12(b)(6) — requiring close attention to the manner in which factual questions are resolved — it . makes sense to treat motions like the one at issue here as Rule 12(b)(6) motions. In addition, Zipes makes it clear that Title VII’s time limits are more like statutes of limitations than like conditions on the court’s subject matter jurisdiction. Although Zipes deals only with the time limit for filing charges of discrimination with the EEOC, see 42 U.S.C. § 2000e-5(e) (1976), its logic extends to the time limit for filing suit after receiving a right-to-sue letter from the EEOC, see-U.S. at-, 102 S.Ct. at 1132,1135. Therefore, Rule 12(b)(6) and its proviso clearly apply, and it would be error to grant a motion to dismiss on factual grounds unresolved by the pleadings.
Fairness, not excessive technicality, is the guiding principle under both Title VII, see Zipes, supra,-U.S. at-, 102 S.Ct. at 1134; Love v. Pullman, 404 U.S. 522, 527, 92 S.Ct. 616, 619, 30 L.Ed.2d 679 (1972), and the Federal Rules of Civil Procedure. The mandatory language in which Rule 12(b)’s proviso is couched underscores the importance of providing plaintiffs with the essential safeguards of summary judgment procedure whenever they face a motion to dismiss that turns on questions of fact. Even under Rule 12(b)(1), procedural safeguards equivalent to those in Rule 56 are required, with Rule 56 used selectively as a guide to ensuring fairness. See Exchange Nat’l Bank of Chicago v. Touche Ross & Co., 544 F.2d 1126, 1131 (2d Cir. 1976); Barrett v. United Hospital, 376 F.Supp. 791, 795 & n.14 (S.D.N.Y.), aff’d, 506 F.2d 1395 (2d Cir. 1974). Where facts material to a jurisdictional time limit are in dispute, both fairness and analogy to Rules 12(b)(6) and 56 require that the court provide the parties a full opportunity to air their factual dispute. Furthermore, they direct the court to take evidence on the question if the parties’ affidavits do not suffice to eliminate all genuine issues of material fact. See Williamson v. Tucker, 632 F.2d 579, 588-589 (5th Cir. 1980).3
The importance of fair procedures in factfinding at any stage requires this ap[361]*361proach, whether or not the parties invoke the precise words in the Federal Rules. Under either Rule 12(b)(1) or Rule 12(b)(6), a court need not consider matters outside the pleadings at all. But once it decides to consult such matters it should so inform the parties and set a schedule for submitting additional affidavits and documents if the parties wish.
Accordingly, since the District Court did not so notify the parties, we may sustain the dismissal only if it meets the stringent standard for dismissal without regard to matters outside the pleadings: “[I]t appears beyond doubt that the plaintiff can prove no set of facts in support of his claim which would entitle him to relief.” Conley v. Gibson, 355 U.S. 41, 45-46, 78 S.Ct. 99, 101-102, 2 L.Ed.2d 80 (1957); see Ware v. Associated Milk Producers, Inc., 614 F.2d 413, 414-415 (5th Cir. 1980) (in context of statute of limitations question). The 90-day limit aside, Gordon pleaded an adequate cause of action under Title VII. Neither her complaint nor her answer to NYWA’s motion to dismiss concedes that she received notice of her right to sue before October 9. Without considering the return receipt, it is hard to imagine how the District Court could address, much less decide, NYWA’s contention that the suit was not timely filed. Therefore, dismissal of Gordon’s case on the pleadings alone could not have been proper.
Given that the District Court clearly considered “the entire record herein,” including matters outside the pleadings, it did not provide plaintiff “reasonable opportunity” to present relevant material. It did not inform the parties that it was considering the motion as if it were a motion for summary judgment, nor did it solicit further submissions on the question of which day Debora Gordon received notice of her right to sue. The debate over possible factual inferences in both parties’ papers should have put the court on notice that it needed a great deal more information before decid- . ing that there was no material issue of fact in dispute.4 Under the mandatory phrasing of Rule 12(b), the court’s failure to provide a fair procedure for submission of affidavits or other factual material is reversible error, even though Gordon did not raise the issue precisely in her opposition to NYWA’s motion to dismiss.
The order dismissing appellant’s case for lack of jurisdiction over the subject matter is therefore reversed, and the case is remanded to the District Court for further proceedings on the issue whether appellant’s suit was timely filed.
Reversed and remanded.