The government appeals from an order entered in the United States District Court for the District of Maine granting, and sustaining upon reconsideration, the defendant’s motion to suppress evidence. That order was entered not on the merits, but by reason of the government's failure to file a timely response to the defendant’s suppression motion. We vacate the order and remand with directions to hear and determine the suppression motion.
I. BACKGROUND
The facts relevant to the disposition of this appeal are largely undisputed. They can be succinctly summarized.
On January 16, 1992, a two-count indictment was returned against defendant-ap-pellee Leslie Roberts. Count I alleged manufacture of more than 1,000 marijuana plants in violation of 21 U.S.C. §§ 841(a)(1), 841(b)(1)(A) (1988 & Supp. II 1990). 1 Count II alleged possession of marijuana with intent to distribute in violation of the same statutes. On Friday, February 21, 1992, Roberts’ counsel filed a substantial motion to suppress evidence, addressing a copy to the prosecution. According to regular office procedure, Friday’s outgoing mail was hand-carried to the post office either that day or the next business day (Monday, February 24). On Monday, defense counsel advised the prosecutor that the motion had been filed and should arrive in that day’s, mail.’ The government never received the mailed papers. On Wednesday, *19 February 26, the prosecutor requested another set. Defense counsel immediately forwarded copies by facsimile transmission.
Under the applicable local rule, objections to filed motions must themselves be filed within ten days. 2 On March 10, the district court, concluding that the response period had elapsed, summarily granted the motion to suppress. Later that same day, the government moved for reconsideration, informing the court that its response to the suppression motion would be filed instanter and explaining that its failure to object at an earlier date resulted from an interpretation of Local Rule 19(c) that differed from the district court’s interpretation.
The next day, the government filed its opposition to the motion to suppress. On reconsideration, the district court accepted the prosecutor’s explanation at face value, finding that the government’s bevue “was the result of a misinterpretation of Local Rule 19 and of ignorance of its precise requirements.” The court, however, decreed that these circumstances constituted neither “good cause” nor “excusable neglect” sufficient to justify relieving the government “from the consequence of untimely filing.” This interlocutory appeal followed. We have jurisdiction under 18 U.S.C. § 3731 (1988).
II. A PROCEDURAL QUAGMIRE
Depending on how one reads the relevant rules, there are several possible ways to assess the extent of the government’s delay. According to the. letter of Local Rule 19(c), the ten-day response period began on “filing,” February 21. Excluding intermediate weekends, see Fed.R.Crim.P. 45(a) (“When a period of time prescribed or allowed is less than 11 days, intermediate Saturdays, Sundays and legal holidays shall be excluded in the computation.”), the government’s objection to the motion was due by day’s end on March 6. The government moved to reconsider on March 10 and filed its objection to the suppression motion on March 11. Under this scenario, then, the government’s motion was four days late and its opposition five days late.
But, there is more. Both sides agree that the government was entitled to an additional three days under Fed.R.Crim.P. 45(e). The rule grants a three-day extension “[wjhenever a party has the right or is required to do an act within a prescribed period after the service of a notice or other paper upon that party and the notice or other paper is served by mail.” Fed. R.Crim.P. 45(e). Local Rule 19(c), however; appears to emphasize filing, not service; and, notwithstanding the parties’ agreement, we think it is an open question whether Rule 45(e) applies in a case where the obligation to act is triggered by filing rather than by service.
Assuming that the local rule is interpreted as allowing an act to be done upon service, 3 thus forcing Rule 45(e) into play, the response deadline is still problematic. The defendant’s, interpretation is that the government would then have had a total of thirteen days within which to file its opposition. Since the prescribed period has now grown to more than eleven days, the defendant argues, intermediate weekends should be included in the count and the government should have filed its opposition no later than March 5. See 3A Charles A. Wright, Federal Practice and Procedure § 755, at 98 (2d ed. 1982). So viewed, the three-day extension is no extension at all; *20 it leaves the government with one less day in which to object than the government would have enjoyed had the motion been served personally — a paradoxical result that frustrates the core purpose of Rule 45(e).
On the other extreme, one might interpret the service-by-mail extension as a period separate and apart from the ten-day response period. After all, each is “a period of time prescribed or allowed [that] is less than 11 days.” Fed.R.Crim.P. 45(a). So construed, weekends would be excluded from the count entirely. On this hypothesis, the prosecution was not tardy at all; its opposition to the suppression motion was not due until March 11.
Perhaps the most sensible way to dispel this cloud cover is to treat the weekend-exclusion provision of Rule 45(a) as applying only to those periods of time in which a party is expected to do something. The three days that Rule 45(e) allots for service by mail is a period in which a respondent is required to do nothing but wait for service. If we were to exclude weekend days from the ten:day response period but count them for the three-day period allotted for mail service, the objection would have been due on March 9, leaving the government only one day behind in moving to reconsider and two days behind in opposing the suppression motion.
The calculations we have been discussing in the three immediately preceding paragraphs are based on the assumption that service, rather than filing, pulls the trigger under Local Rule 19(c), thus implicating Rule 45(e). On that assumption, the litany of problems is by no means finished. “Service by mail is complete upon mailing.” Fed.R.Civ.P. 5(b). In retrospect, defense counsel cannot say whether the motion was actually mailed on Friday, February 21, or on Monday, February 24. If the ten-day response period and the three days for service by mail are counted from February 21, the government was probably in arrears; if those periods are counted from February 24, or if the actual receipt of the documents by facsimile transmission on February 26 constituted service, then the government probably did not miss its deadline at all.
In the midst of this babelism, one thing is perfectly plain: the district court’s order ought to be vacated. 4 Viewing the record in the light most favorable to the defendant, and making almost every intermediate interpretive decision in his favor — we except only the counter-intuitive paradox discussed supra p. 19-20 — the government moved to reconsider no more than four days after its opposition to the suppression motion was due and filed the opposition on the very next day. Even assuming, ar-guendo, this worst-case scenario — an assumption on which we base the remainder of our ■ opinion — the ruling below cannot pass muster.
III. STANDARD OF REVIEW
A district court possesses great leeway in the application and enforcement of its local rules.
See United States v. Diaz-Villafane,
*21
In making discretionary judgments, a district court abuses its discretion when a relevant factor deserving of significant weight is overlooked, or when an improper factor is accorded significant weight, or when the court considers the appropriate mix of factors, but commits a palpable error of judgment in calibrating the decisional scales.
See Independent Oil and Chem. Workers of Quincy, Inc. v. Procter & Gamble Mfg. Co.,
IV. ANALYSIS
This appeal arises in a peculiar procedural posture. Ordinarily, a district court faced with a motion to reconsider must apply an interests-of-justice test. In
Greene v. Union Mut. Life Ins. Co.,
The wrinkle that distinguishes this case is that, rather than denying the motion to reconsider, as in Greene, the court below granted the motion to reconsider but then affirmed its original ruling. See supra note 5. It can be argued that, in so doing, the court treated the motion to reconsider as a motion for an extension of time, thus bringing Fed.R.Crim.P. 45(b)(2) to the fore. 6 Rule 45(b)(2) provides that when an act is required to be completed within a specified time, the court “for cause shown” may, “upon motion made after expiration of the specified period,” extend the deadline if the movant’s failure to act resulted from “excusable neglect.”
We do not choose to enter into a purely academic debate over the controlling standard. Excusable neglect is a flexible concept. In this case, as we demonstrate below, its parameters are informed by, and roughly congruent with, the interests of justice. (It would, after all, make very little sense to allow reconsideration because justice requires, only to reassess the underlying procedural default on some standard totally divorced from the interests of justice.) Hence, we proceed to analyze the lower court’s rulings under both rubrics, mindful, withal, that in the end the two standards coalesce.
A. Interests of Justice
Justice is an ideal that defies precise definition. It is, therefore, impossible to list a series of integers that will necessarily dominate the interests-of-justice equation in every case. We can, however, offer certain rules of thumb to guide the district courts.
In determining this motion to reconsider the court’s response to the belated filing before us, it would have helped had the district court examined the following seven factors: (1) the nature of the case, *22 (2) the degree of tardiness, (3) the reasons underlying the tardiness, (4) the character of the omission, (5) the existence vel non of cognizable prejudice to the nonmovant in consequence of the omission, (6) the effect of granting (or denying) the motion on the administration of justice, and (7) whether the belated filing would, in any event, be more than an empty exercise. We emphasize these particular factors because they assist in demonstrating that there was no reasonable basis for the district court to deny the government’s request. The list is merely illustrative. We do not say that courts must necessarily look at each and all of these factors in every case, or that courts cannot, in a proper case, examine other factors. At any rate, the list of factors will require tailoring to reflect the nature of the ruling that underlies the motion to reconsider. Because an interests-of-justice test covers considerable ground, the trial court should strive to acquaint itself with the totality of the relevant circumstances. By the same token, an appellate court called upon to review such a determination must take a panoramic view. We do so here.
1.
Nature of the Case.
This is a criminal case and, importantly, a criminal case involving serious accusations. The defendant was charged with manufacturing marijuana and with possessing it for the intended purpose of commercial distribution. There is a strong public interest in adjudicating felony cases on the merits.
See Hastings,
2.
Degree of Tardiness.
The length of a supplicant’s delay is often a key factor in deciding whether to permit a pleading to be filed out of time. The longer a litigant dawdles, the less incentive exists for a court to reconsider.
See In re Sun Pipe Line Co.,
3.
Reasons for Tardiness.
We look next to the reasons underlying the procedural default. The district court credited the prosecutor's explanation, but adopted a dismissive attitude, literally and figuratively, discerning no excusable neglect. We question the supportability of this conclusion. As we have pointed out,
see supra
Part II, the interlocking rules that govern computation of time in this situation are freighted with ambiguity. Bearing in mind that good cause “is a mutable standard, varying from situation to situation,”
Coon v. Grenier,
4.
Character of the Omission.
In determining whether to hold a litigant to a nonjurisdictional procedural default, the presence or absence of willfulness is invariably a salient consideration.
See, e.g., Velazquez-Rivera v. Sea-Land Serv., Inc.,
In this case, the government’s delay was not intentional. It resulted from a simple mistake — one that was fully understandable in light of the local rule’s ambiguity. The omission was not a byproduct of bad faith or reckless disregard of responsibilities owed to the court.
8
We have said in an analogous context that “[r]andom negligence, while not to be condoned, is less blameworthy than purposeful misconduct.”
Hastings,
5.
Prejudice.
We next inquire whether the interlude caused cognizable prejudice.
See Velazquez-Rivera,
6.
Institutional Interests.
The court, too, has a significant interest in the punctilious observation and strict enforcement of its procedural rules, including temporal requirements.
See In re Sonoma V,
7.
Utility of the Pleading.
We have indicated in related settings that weight should be attached to the likelihood of success if the party moving for reconsideration is allowed to revisit the underlying issue.
See Mackin v. Boston,
8. Recapitulation. The clear majority of the pertinent factors (perhaps as many as six out of seven) militates in favor of reconsideration and reversal. The defendant has identified no countervailing factors and we can think of none. Indeed, the balance of justice seems to weigh more heavily in this case than in Greene (a case in which the movant was afforded some relief). Greene was six days late in responding to a defense motion; here, the government, if late at all, fomented an even shorter period of delay. Moreover, this is a criminal, not a civil, case; and unlike Greene, appellant proffers sympa *24 thetic reasons for its tardiness. 9
B. Excusable Neglect
If we treat the lower court’s ruling as the functional equivalent of a refusal to allow the government to file an opposition out of time, the defendant fares no better. Since Fed.R.Civ.P. 6(b)(2) uses language virtually identical to that of Fed.R.Crim.P. 45(b)(2), decisions construing the civil rule are instructive in determining what constitutes cause or excusable neglect under its criminal analogue. See Fed.R.Crim.P. 45 advisory committee note (1944) (explaining that because Criminal Rule 45 “is in substance the same as [Civil Rule 6] ... matters covered by this rule should be regulated in the same manner for civil and criminal cases”); 3A Wright, supra, § 751, at 92-93 (stating that Civil Rule 6 “may usefully be consulted in determining the meaning of [Criminal Rule 45]”).
In general, mistake or inadvertence as to the meaning of a rule is not a sufficient reason to grant a belated application for more time.
See, e.g., Spear, Leeds & Kellogg v. Public Serv. Co.,
Moreover, case law in this circuit and beyond reveals that the excusable neglect standard, in a situation like this one,
10
embodies a need to consider a matrix of factors not materially different from those we have canvassed in connection with the interests-of-justice standard,
e.g.,
the significance of the delay,
see Coady v. Aguadilla Terminal Inc.,
C. Totalling the Account
We do not think it makes a difference in this case which standard the district court applied (or should have applied). The excusable neglect standard often acquires an “interests of justice” gloss.
See Coady,
Given the collocation of circumstances, we believe that the district court, on either standard, abused its discretion in two ways. First, the court apparently failed to weigh all the proper factors in reaching its decision. Beyond this likelihood, we are convinced that, in granting the suppression motion pro forma and adhering to its order *25 after receiving a credible explanation of what had gone wrong, the court below committed a mistake of judgment that cannot be allowed to stand. When the appropriate elements are placed on the scale, the balance tips dramatically in favor of reconsidering and allowing the opposition to be filed. Put another way, the government showed sufficient cause to excuse its failure to respond more celeritously to the suppression motion.
V. CONCLUSION
We need go no further. 11 This is a serious criminal case. At the very worst, the government inadvertently missed a filing deadline in a situation where a miasma of doubt surrounded the proper interpretation and interplay of the relevant rules. Hence, the government had a plausible reason for the error. It informed the court immediately upon recognition of its possible mistake and filed the omitted response the very next day (no more than five days after it was due). The record reveals no history of recalcitrance, sloppiness, or sharp practice on the government’s part. There is no suggestion of cognizable prejudice to the defendant or burden to the court’s schedule. In these circumstances, stony adherence to the district court’s debatable interpretation of Local Rule 19(c) was unwarranted.
Vacated and remanded.
Notes
. 21 U.S,C. § 841(a)(1) criminalizes,
inter alia,
the "manufacture” of "a controlled substance.” We have recently held that growing marijuana falls squarely within this proscription.
See United States v. One Parcel of Real Property (Great Harbor Neck),
. We are of the opinion that a protocol in which service, rather than filing, triggers the obligation to respond would be far more conventional — and far more logical. Rules requiring a response within a specified period after service or notice abound. E.g., Fed.R.Civ.P. 12(a) (answer to complaint, cross-claim, or counterclaim), 12(e) (response to order for more definite statement), 45(c)(2)(B) (objection to subpoena); Fed.R.Crim.P. 12.1(b) (response to alibi defense), 12.3(a)(2) (reply to demand for witness list), 32.1(b) (objection to probation terms). Calculating a response period from the date of service or notice is a commonly used device because such a paradigm prevents a party from forfeiting an objection to a motion or other pleading about which it had no knowledge.
. We think it is equally plain that the district court’s local rule should be clarified. Literal application of the rule as written would, in many cases, prove unfair to litigants. Specifically, the district court should consider amending the local rule to state clearly whether a response is due from date of filing or date of service and, if the former, what the consequence of lack of notice to the respondent entails. We also hope the district court will clarify that weekends are to be excluded from the computation of the ten-day response period. Finally, the court may wish to clarify whether the three-day period provided in Rule 45(e) can extend the ten-day limit and, if so, whether those additional three days exclude weekends.
. As a technical matter, the court below agreed to reconsider but then refused to alter its earlier
*21
order. This maneuver does not affect the standard of review. The denial of a motion for reconsideration is reviewable for abuse of discretion.
See Odishelidze v. Aetna Life & Casualty Co.,
. By contrast, in
Greene
we specifically noted that Fed.R.Civ.P. 60(b), with its "excusable neglect” standard, did not apply because the defendant had moved merely to dismiss certain counts, not to dismiss the entire case.
Greene,
. We understand that, in granting the defendant's motion, the district court did not dismiss the indictment, but instead suppressed evidence. The government has argued, however, that the material suppressed — the government’s entire storehouse of physical evidence (including 2,577 marijuana plants, eight firearms, a substantial sum of money, etc.) and evidence of the defendant’s admissions of guilt — is of such importance that, unless the order is vacated, the case - cannot be successfully prosecuted. The defendant has not disagreed with this assessment. Hence, we regard the order appealed from as the functional equivalent of an order for dismissal.
. Indeed, the record reveals that diligence, rather than dilatoriness, typified the government’s behavior. The government was prompt in notifying the defendant that it had not received the relevant documents, in reporting its position to the court as soon as it was notified that the court considered the response period to have expired, and in filing a reply to the suppression motion immediately thereafter.
. In
Greene,
plaintiffs counsel said that he was "on 'quasi-vacation,' ’’ that he “ ‘misunderstood’ defendant’s counsel,” and that “his office procedures broke down.”
Greene,
. The Ninth Circuit, in an analogous context, urged lower courts to "apply[ ] a liberal definition of ‘excusable neglect’ ” and suggested a broad range of factors that might properly be considered in attending to the task.
In re Mago-uirk,
. Because we conclude that the district court abused its discretion in failing to reconsider and accept the government’s opposition out of time, we need not address the government’s contention that, notwithstanding the lack of a timely opposition, the district court was nevertheless required to review defendant’s motion on the merits before suppressing the evidence.
